Migration fixes

This set of changes should fix any remaining issues with schema simplification migrations. I've been able to successfully migrate Yale and Clark to the new schema without any issues, though first you have to run the following fake migrations:
```bash
python manage.py migrate cal 0001_initial --fake
python manage.py migrate qsd 0001_initial --fake
python manage.py migrate qsdmedia 0001_initial --fake
python manage.py migrate survey 0001_initial --fake
python manage.py migrate cal 0002_create_email_reminder --fake
```