Also, I replaced a number of tearDown methods with addCleanup instead.
And also remove some unneeded patch.stopall() calls.

Make donations configurable

Added donation button to dashboard

Generalize merchant defined data for payment processor

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]