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