Eox-tagging

Added

- Added expiration_date, tag_value and tag_type filters.

Changed

- Fixed courseenrollments filters and refactor the rest.
- Removed `required` from access field in serializer.

Added

- Permissions compatibility with DOT.

Added

- Migration compatibility with PY35.

Changed

- Fixed not loading correct settings when testing.

Added

- Added support for filters in django2.2

Added

- Added support for Django 2.2.