Please note that this is a squshed commit and the work of:
Symbolist, macdiesel, nedbat, doctoryes, muzaffaryousaf and muhammad-ammar

Add a django-rest-framework APIView that supports reading/writing the current value of a configuration model

Also remove useless docstrings where they were added to keep pylint
quiet.

ConfigurationModels can be managed using the admin site. They are
append-only, and track the user who is making the change, and the time
that the change was made. The configuration is stored in the database,
and cached for performance.

[LMS-1220]