Enable sh emulation for Zsh and allow loading modules recursively.

spack module :
- refresh accepts a constraint
- find and refresh share common cli options
- ask for confirmation before refreshing
- deleting the module file tree is now optional

Updated the 'scotch' package to use oneline 'variant' directives.

Updated the Scotch package to conform to PEP8 standards and to test style checking improvements.

- was missing the obvious.

- Exempt overlong URL lines from checks.
- Omit some of the more painful PEP items.

I addressed them by factoring the code better to follow the visitor
pattern.  This will allow actions to be easily added in the future.
These may not even be file sytsem views.  One could add actions to
generate shell init scripts, JSON DAG-dumpers, GraphViz DOT file
generators, etc (yes, some of these are alread in there - just to give
the idea).

Also added is a top-level test

 $ source share/spack/setup-env.sh
 $ ./share/spack/examples/test_view.sh

Read the top of that script first.

remove the part I added to setup-env.sh as this does not work unless the modules package is already built.

Yay for non-portable declaration syntax.  After the previous screwiness
I ran this through a number of shells, and found that this is the most
portable version I coudl seem to get.

This reverts commit 496e4856.

Undo overly large set of changes -- LLVM wasn't ready.  Tom can
recommit just the zsh stuff.

fixes #284

The setup-env.sh script now saves off the argument array before shifting off
all the arguments so that the final command invocation doesn't arbitrarily
requote the arguments.  All external quoting is preserved now.  This has been
thoroughly tested with zsh, but should probably be tested with bash etc.
before acceptance.

- Better shell support for cd'ing into directories
- Fix some csh weirdness with nested aliases.

- csh scripting is a GIANT pain in the ass
- hopefully the thin script layer doesn't get much more complex.

- One file with all the module classes (spack/modules.py)
  - Has an EnvModule superclass that does most of the work and consolidates common code
  - Subclasses have specializations for different module systems (TclModule, Dotkit)

- One command (spack module) for all the types of modules to use
  - the one command is used by the scripts, only need to maintain in one place
  - has some subcommands for different module types, but they're handled mostly generically.

- Consolidate zsh support into a single setup-env.sh script.