Spheral banner & CMake git dependency

[mdavis36]

The current Spheral banner displays as such
Spheral version : <Branch> <Hash> <# of all time commits>
We would like to display it as
Spheral version : <Last release version> <# of commits from last tagged release> <Branch> <Hash>
And when the .git folder is not available we would like:
Spheral version : <Last release version>

This should be done by guarding git calls within CMake when repository information is not present.
CMake also currently depends on repo data to generate the list of test files to install, we need to find a way around this without .git.

This will resolve issue #207