Adding teachers field to ClassSubject (untested).

Changing most things that depend on knowing the teachers of a class.
Some caching .depend_on_* still need to be updated.
Removing unused ClassSubject method time_created
More changes related to the teachers field.
Fields and migrations for ClassSubject and Program.
Data migrations and small fixes for ClassSubject

Migrations fill in the teachers and title field for ClassSubject.
Some small fixes with those fields as well.
Record model to store when a user completes an action.

This is to replace using userbits for such things as completing a survey,
or the teacher quiz, attending a program, etc.
More things converted to Record; migrations; small teachers fixes.
Changing user roles to be django groups
More changes with user roles
ESPUser admin clean-up and bugfixes for user roles.

Also removing accidentally-commited, non-functional code.
Data migration to convert user roles
Bugfixes and test updates for program and user
Minor update to program creation logic
Bugfix with anonymoususer's groups
Minor changes to the admin panel for ClassSubject
Adding a permission model and some conversions to it.
Beginnings of moving deadlines to permissions
Changing isAdmin to accept a program instead of anchor
Deadline logic during program creation
Bugfixes