Moved the Add function to the details page

1. Reworked Remove so the extra url parameter is no longer necessary
2. Reworked BaseController to provide increased ease-of-use
3. Significantly simplified TasksController using new BaseController
methods
4. Added additional Metadata to work with new BaseController methods
5. Renamed _SomethingEdit to _SomethingActions, and moved the Details
link into the partial View
6. Reworked _AddAssignment and added _RemoveAssignment to work for all
M-to-N relationships
7. Converted SelectLists to strongly typed
8. Improved layout of Details View