llvm trunk version

Adding a trunk version to the llvm package.  This has all the features
and requirements of the others, with the additional caveat that the llvm
project makes no guarantee that trunk on all repositories together will
necessarily make a working compiler.  It has been tested, and worked
with a version today, but not yesterday, so if you test keep that in
mind.

openssl : url computation

refactoring proposal : composite for Stage and FetchStrategy 

Compiler detection was not getting triggered properly with some of the
new config logic.  Adjust the conditions under which Spack will serach
for compilers.

remove the unprotected key name from create.py

Small fix to use dicts correctly.

Add Mesh Packages: Crypto++, Exodus II, ndiff, TetGen, and Triangle

Added the "+static" variant to "hdf5" to enable "ExodusII" support.

Remove unnecessary URLs

Add latest version

libedit depends on ncurses

Use hash to make shorter module and dotkit names, fixes #433

Added package : Quantum Espresso

Paraview fix

Bugfix: netlib-scalapack does not work with all versions of python

RPATH was collecting all lib from all dependencies, when dep tree is deep like in ParaView the path was growing too much, showing install problems  now just direct dependencies rpath is added

- Recent external repo refactoring made `repo_for_pkg` raise an error
  when the package was not known.

- Correct behavior is to return the highest precedence repo.