ProctorModuleInfo: raise exception if course DNE
ProctorModuleInfo: add submission_history method

This is similar to courseware.views.submission_history except that:

1. It works for a list of locations and returns a dictionary rather than a Fragment
2. It filters StudentModuleHistory to those that have 'attempts' in their state.
3. It strips any duplicate (ie identical state) StudentModuleHistory entries.
4. It propagates all exceptions
add 'Submission History' to proctor admin panel

Staff users can now navigate to a problem, click 'Proctor Submission
History' button in the proctor admin panel, type a username and view
the user's attempts for each problem they've attempted within the
problem bank.