Keep adding unit tests

[rcarson3]

It would be useful to make use of BLT's google test inclusions to test and make sure we don't see any regressions when things are added.

The PA_test is pretty much there it just needs to be swapped over to make use of google test. Next, a single xtal tension example that's 5x5x5 should allow us to test our voce and mts models and make sure no major changes are introduced. We should test our full and PA formulations here. During all cases, the debug device option should be used to make sure our code memory wise works on both GPUs and CPUs.

[rcarson3]

Initial GTest support added in cdc6712

Work still needs to be done to add full simulation tests and check those results.

[rcarson3]

The unit tests have been updated and now we have a python driver for some of the full simulations tests as of 9af0de4

I'm going to keep this issue open as we can always add additional tests to ensure we have proper testing of our code base.