Feature/instructor interface

This PR:
- makes changes to the admin interface (displays users for the Users_Collections model; displays email addresses instead of openiduser numbers)
- displays add course button for instructors (staff members) and super users only
- creates a Users_Collections object when a new collection is created by an instructor/super user
- displays edit functionality only for the collections the logged in instructor created
- displays edit functionality for all the collections for the super users

Super users can make the instructors staff members from the admin interface. 
The staff members don't have the permission to make edits from the admin interface (their permissions can be modified though).

Moreover, this PR:
- implements the edit and student view functionality for instructor interface