* Add packaging tutorial to docs

* packaging tutorial: formatting

This adds the built recipe for
[Jansson](http://www.digip.org/jansson/),
*a C library for encoding, decoding and manipulating JSON data.*

GitHub Repo: https://github.com/akheron/jansson

Downstream Usage:
  In [ISAAC](https://github.com/ComputationalRadiationPhysics/isaac)
which is an *in situ visualization library* based on
  [alpaka](https://github.com/ComputationalRadiationPhysics/alpaka)
and/or CUDA which is used in
  [PIConGPU](https://github.com/ComputationalRadiationPhysics/picongpu).

This adds the built recipe for
[libwebsockets](https://libwebsockets.org/lws-api-doc-master/html/index.html),
a *C library for lightweight websocket clients and servers*.

GitHub Repo: https://github.com/warmcat/libwebsockets

Downstream Usage:
  In [ISAAC](https://github.com/ComputationalRadiationPhysics/isaac)
which is an *in situ visualization library* based on
  [alpaka](https://github.com/ComputationalRadiationPhysics/alpaka)
and/or CUDA which is used in
  [PIConGPU](https://github.com/ComputationalRadiationPhysics/picongpu).

* Allow compiler wrapper to modify environment

This adds the ability to set environment variables in the compiler
wrappers. These are specified as part of the compilers.yaml config.
The user may also specify RPATHs in compilers.yaml that should be
added.

* Minor doc tweak

Adding some lines to prevent from using any CUDA stuff, if NVIDIA CUDA Developement Kit was installed before.

* Added version 1.5.3 for py-matplotlib

* Updated url to pypi.io so all versions are properly downloaded.

Added 'lib64' directory as a possible option where tclConfig.sh file can be found.

* fix tau installation issue : setup_environment() is
called before install phase when 'Makefile.*' doesn't
exist (causing list index out of range error).

* Added detailed comment suggested by @alalazo

Updated python package reflecting the changes in 9347f869

* Waste less space when fetching cached archives, simplify fetch messages.

- Just symlink cached files into the stage instead of copying them with curl.
- Don't copy linked files back into the cache when done fetching.

* Fixes for review.

* more updates

* last update

- This might be useful but we don't want to do it unconditionally.

Not the desired eventual behavior, but cflag subset matching is not currently working for anonymous specs and this provides a temporary solution by restricting the feature until it is fixed.

* Wordsmithing/minor-edits to module tutorial

A small set of wordsmithing, spell checking and minor edits to the fancy
new modules tutorial!

* Fix typo (sneaky z key...)

* Fix "S:" and "manual<" typos

* Add PFFT parallel FFT package

* pfft: fix non-double precision

* mpich: updated package to build_systems

* qa : flake8 issues

* fix bug in search for concrete compiler

* simplify implementation of concretize_compiler

* fix flake8 errors

* Add STAR-CCM+ package

* Cleanup commented out code

* November 1 seems to have brought a new texlive release, updating the
digest to match.

Also switching the url from their automagic mirror to an explicit
site to avoid inconsistencies during their updates.

It seems like only yesterday (#2073) that I updated this....

* Add comment to url warning about mirror updates

Add a comment to the download info warning to use a
specific site rather than the mirror, to avoid wobbles
during their asynchronous updates.

* Fix typo ('to no' -> 'do not')

Some packages which include resources fetched from source control
repositories terminated package installs because they failed to
archive; specifically, this included all SCM resources which identify
a specific state of the repo - for example a revision in svn or a
tag/revision in git. This is because the resource stage creation
logic did not choose an appropriate archive name for these kinds of
resources.

* Set OS-specific default compilers

* Fix flake8 warnings

* Use code from the `distro` package to improve linux distro detection.

Various issues [1] [2] with the platform.linux_distribution function led
to the function being deprecated in python 3.4. The pipi package distro
[3] contains compatible improved code that better tracks current methods
for identifying linux distributions (see, for example, [4],[5]).

[1]: https://bugs.python.org/issue20454
[2]: http://bugs.python.org/issue1322
[3]: https://pypi.python.org/pypi/distro
[4]: https://refspecs.linuxbase.org/LSB_3.0.0/LSB-PDA/LSB-PDA/lsbrelease.html
[5]: https://www.freedesktop.org/software/systemd/man/os-release.html

* fix (potential) unicode problems

* libSplash: Add 1.6.0 Release

Add the latest release of libSplash, version 1.6.0.

* Fix flake8 checks (another loop inversion issue)

* module files tutorial : first complete draft

- first complete draft for module files tutorial
- minor corrections to module file reference

* module file tutorial : first batch of corrections

- module avail spelled out fully
- typos from @adamjstewart
- rewording of a few sentences

* module file tutorial : first batch of corrections

- emphasized lines in yaml files

* module file tutorial : fixes according to @citibeth and @adamjstewart reviews

- used long format for command options
- reworded unclear sentence on tokes
- reworked table in reference manual to make it clearer

* module file tutorial : implemented corrections collected on site from @schlyfts

* module file tutorial : removed comment (@hartzell suggestion)

* updates to matio package

- update to a AutoTools package
- add variants for hdf5 and zlib
- add latest version

* fix flake8 error

* fix and simplify opencoarrays package using new CMakePackge methods

* add new version

* Add options for hashes, tree depth, and YAML to `spack spec`.

- Can now display hashes with `spack spec`, like `spack find`.
  - Removed the old "ids" argument to `spack spec` (which
    printed numerical values)b

- Can output YAML spec from `spack spec` with `-y`

- Can control depth of DAG traversal with --cover=[nodes|edges|paths]

- Can print install status (installed, missing, not installed) with -I

* Don't use YAML aliases in specs.

- Force Spack's YAML dumper to ignore aliases.
- aliases cause non-canonical YAML to be used in DAG hash, and result in
  redundant hashes.
- add a test to ensure this behavior stays