added basic tests for management

I've added some tests for management.py.
One checks that the correct paths are read in for the modules and courses.
The other checks that the defaults are used if an invalid settings file is used.

The idea is to test every possible use of each function, and then check the impossible ones to make sure it breaks in the correct way. More tests need to be added ideally before more functionality is added.

If anything is unclear please let me know