Add auditlog to Django

[schmave]

Closes DEM-24

• Add change tracking for some interesting models that don't currently have good change tracking. Changes to these models (from Python code only, not Java) will be tracked:
  • AttendanceCode
  • AttendanceRule
  • NotificationRule
  • Person
  • RoleRecord
  • Tag
  • User
• Added a bunch of models to the Django admin interface
• Added a link to view the change history for a particular model from the admin interface:

* You can access the history of changes to an object using `foo.history`, as described in more detail in the [auditlog docs](https://django-auditlog.readthedocs.io/en/latest/usage.html#object-history)