* Porting: substitute nose with ytest

This huge commit substitutes nose with pytest as a testing system. Things done here:

* deleted external/nose as it is no longer used
* moved mock resources in their own directory 'test/mock/'
* ported two tests (cmd/find, build_system) to pytest native syntax as an example
* build_environment, log: used monkeypatch instead of try/catch
* moved global mocking of fetch_cache to an auto-used fixture
* moved global mocking from test/__init__.py to conftest.py
* made `spack test` a wrapper around pytest
* run-unit-tests: avoid running python 2.6 tests under coverage to speed them up
* use `pytest --cov` instead of coverage run to cut down testing time

* mock/packages_test: moved mock yaml configuration to files instead of leaving it in the code as string literals

* concretize.py: ported tests to native pytest, reverted multiprocessing in pytest.ini as it was creating the wrong report for coveralls

* conftest.py, fixtures: added docstrings

* concretize_preferences.py: uses fixtures instead of subclassing MockPackagesTest

* directory_layout.py: uses fixtures instead of subclassing MockPackagesTest

* install.py: uses fixtures instead of subclassing MockPackagesTest

* optional_deps.py: uses fixtures instead of subclassing MockPackagesTest

optional_deps.py: uses fixtures instead of subclassing MockPackagesTest

* packages.py: uses fixtures instead of subclassing MockPackagesTest

* provider_index.py: uses fixtures instead of subclassing MockPackagesTest

* spec_yaml.py: uses fixtures instead of subclassing MockPackagesTest

* multimethod.py: uses fixtures instead of subclassing MockPackagesTest

* install.py: now uses mock_archive_url

* git_fetch.py: uses fixtures instead of subclassing MockPackagesTest

* hg_fetch.py: uses fixtures instead of subclassing MockPackagesTest

* svn_fetch.py, mirror.py: uses fixtures instead of subclassing MockPackagesTest
repo.py: deleted

* test_compiler_cmd.py: uses fixtures instead of subclassing MockPackagesTest

* cmd/module.py, cmd/uninstall.py: uses fixtures instead of subclassing MockDatabase

* database.py: uses fixtures instead of subclassing MockDatabase, removed mock/database

* pytest: uncluttering fixture implementations

* database: changing the scope to 'module'

* config.py: uses fixtures instead of subclassing MockPackagesTest

* spec_dag.py, spec_semantics.py: uses fixtures instead of subclassing MockPackagesTest

* stage.py: uses fixtures instead of subclassing MockPackagesTest. Removed mock directory

* pytest: added docstrings to all the fixtures

* pytest: final cleanup

* build_system_guess.py: fixed naming and docstrings as suggested by @scheibelp

* spec_syntax.py: added expected failure on parsing multiple specs closes #1976

* Add pytest and pytest-cov to Spack externals.

* Make `spack flake8` ignore externals.

* run-unit-tests runs spack test and not pytest.

* Remove all the special stuff for `spack test`

- Remove `conftest.py` magic and all the special case stuff in `bin/spack`

- Spack commands can optionally take unknown arguments, if they want to
  handle them.

- `spack test` is now a command like the others.

- `spack test` now just delegates its arguments to `pytest`, but it does
  it by receiving unknown arguments and NOT taking an explicit
  help argument.

* Fix error in fixtures.

* Improve `spack test` command a bit.

- Now supports an approximation of the old simple interface
- Also supports full pytest options if you want them.

* Use external coverage instead of pytest-cov

* Make coverage use parallel-mode.

* change __init__.py docs to include pytest

* Allow exclusion of packages from `spack module loads`

* Comment out excluded packages instead of not showing them at all.

* inheritance of directives: using meta-classes to inject attributes coming from directives into packages + lazy directives

* _dep_types -> dependency_types
* using a meta-class to inject directives into packages
* directives are lazy

fixes #2466

* directives.py: allows for multiple inheritance. Added blank lines as suggested by @tgamblin

* directives.py: added a test for simple inheritance of directives

* Minor improvement requested by @tgamblin

CMakePackage: importing names from spack.directives
directives: wrap __new__ to respect pep8

* Refactoring requested by @tgamblin

directives: removed global variables in favor of class variables. Simplified the interface for directives (they return a callable on a package or a list of them).

* init yorick package

* attempt at picking up SPACK's compiler choice, todo ~X variant.

* sphinx docstring error ?

* version# tarball, ~X default, docstring fix

* sphinx docstring fix(?)

The upstream luafilesystem tarball/version had a wayward/inconsistent
underscore in their more recent version tag.  The played badly with
our package fetching machinery (due to recent changes?).

Upstream cleaned up their bit which required some touchups here.

- updated the url
- updated the version (digest)
- updated the format statement for the path to the rockspec.

* Adds catch, cppunit, spdlog, tinyxml(1 and 2), google benchmark

Tinyxml comes in two flavors, 1 and 2. Each comes in several
versions... So they cannot be easily united into a single package.

* Use CMakePackage and friends, add copyright

Also eleminate debug/release variants, since it no longuer fits in the
CMakePackage format.

* Remove unnecessary url

* spdlog now has tagged releases

* Remove unnecessary url argument

* Fewer quotes in cmake args, because magic

* Incorrect base class for tinyxml

* Ensure that every package has a license

Also fixes URLs with http://http:// doubled.

This is a continuation of #2656.

* Add license to every file in Spack

* Make sure Todd is the author of all packages

* Fix flake8 tests

* Don't license external Sphinx docs

* Don't display licenses in tutorial example packages

Also fixes typos and converts command-line examples
from tcsh to bash, which is more common

That's because in set_build_environment_variables()
the funciton filter_system_paths() is actually applied to
package prefixes, and not to prefix/lib or prefix/include.

- `-t` | `--types` argument now shows deptypes in `spack spec`

sigh.

* Remove usernames from paths in docs

* Fix path export

* Added uuid: OSSP uuid is a ISO-C:1999 application programming interface

* Fixed install error in cmor package

* Added uuid: OSSP uuid is a ISO-C:1999 application programming interface

* Fixed install error in cmor package

* Modifiying fontconfig file to allow install in OpenSuse 13.2

* Adding pkg-config dependency to freetype and libxml2

* Removed first possible solution. With @adamjstewart selecting the one adding pkg-config to dependencies

Small fix for the homepage of the package libspatialindex.

The primary goal of #2292 was to use the frontend compiler to make
build dependencies like cmake on HPC platforms. It turns out that
while this works in some cases, it did not handle cases where a
package was a link dependency of the root and of a build dependency
(and could produce incorrect concretizations which would not build).

Trilinos dependency is very heavy, the zoltan one is light. I'm not sure
if there is a situation where one needs the former.

* Update digest for vim@8.0 tarball.

The digest appears to have changed.

The new digest value matches the value in their
[MD5SUMS](ftp://ftp.vim.org/pub/vim/unix/MD5SUMS)
file.

* Change ftp.vim.org -> github.com/vim/vim/archive

Vim seems to do weekly releases, but the name of the tarball on
ftp.vim.org doesn't change so we have to regularly play 'update the
digest' (aka Internet whack-a-mole).

This commit changes the url so that we are now downloading particular
versions from the Vim project's github archive.

I didn't walk back through of time to get all of the versions that
used to be explicit.  I grabbed the final `7.4` and the current `8.0`
releases.  If people need more we can add them.

* Better output for disambiguate_specs()

* Fix wrong exception name.

* Fix satsifies(): concrete specs require matching by hash.

- Fixes uninstall by hash and other places where we need to match a
  specific spec.

- Fix an error in provider_index (satisfies() call was backwards)

- Fix an error in satisfies_dependencies(): checks were too shallow.

* Fix default args in Spec.tree()

* Move installed_dependents() to DB to avoid unknown package error.

* Make `spack find` and `sapck.store.db.query()` faster for hashes.

* Add a test to ensure satisfies() respects concrete Specs' hashes.

* Add gawk, GNU awk.

* flake8 fix.

* Add package for fastqc

This tool is a java mess.  Their Way To Do It is to just copy the entire
tree into it's final resting place, make the perl script at the top
level executable and take it from there.

Yuck.

This package assumes that `set_executable` actually sets all the user
bits.  If that change doesn't go in, then something equivalent needs to
be done.

* Use chmod to make fastqc executable

I haven't gotten any feedback on changing set-executable, so switch to
using chmod (from the cuda package).

* Flake8 cleanup

* Install files neatly, don't just copy top level of dir

Rather than blindly copying everything in the distribution, carefully
put the necessary bits into reasonable places.  Neatness counts, etc...

This requires patching the `fastqc` perl script, so this commit adds a
patch file.

* Additional pep8 cleanup

* Let dependency handle adding jdk to PATH

* Flake8 cleanup

* Ensure that java is on PATH

I thought that the run dependency on the jdk would put
java on my PATH, but it does not appear to work.

For now, do it by hand.

* Customization for make targets in build and test phases for AutotoolsPackage

* Updated Blitz++ to use customized make build and test targets

* Removed flake8 error

* Removed make test customization, added make install customization, need to figure out issues with multiple make targets

* Changed build_targets and install_targets to normal attributes

* py-markdown: Add new package for python-markdown.

* py-markdown: Added restrictions on Python version.

* py-markdown: Removed upper-limit on compatible Python versions.

* py-markdown: Reinstated upper bound on Python version. Also fixed small formatting error.