Add unit test framework to OpenOrb (our adopted orbit integration engine).

This includes: 

• A make target so running 'make test' will execute all unit and integration tests
• A few example unit tests (for versioning functionality)
• Running the python/test.py integration test

Unit test framework will use pytest. The idea is that all code (including command line utilities) will be tested via pytest drivers (to maintain uniformity).

The work will be on https://github.com/mjuric/oorb/tree/build-system-rework, and will be PR-ed upstream upon completion.