Initial unit testing framework and tests. (#7026)
This adds an initial unit testing framework, including necessary changes for SCons and AppVeyor. It also adds some tests for the cursorManager module, which serve both as useful tests and as an example of how this can be used.
Unit tests and infrastructure are located in the tests/unit directory. See the docstring in the tests/unit/__init__.py file for details.
You can run tests using "scons tests". See the "Running Tests" section of readme.md for details.
