Nalanda RCT3 Cleanup

Summary of changes:
* Display total correct when quiz completed.
* Switch StoreItem over to non-Django model.
* Award points for questions answered correctly on quizzes (based on server side basepoints).
* Increases seed across all items in a test so that no two items in a test have the same seed.
This was intended as more of a double check, but does have that side effect as well. So seems that separating can be helpful. The boolean flag is about everything that ever happened, while the number is about what you can earn right now.