Finished up core group management.

- Working on memberships. Create is causing issues for testing membership.
Can no longer add duplicate group member.
Adding and removing members implemented.
Repo add/remove, some permission CRUD implemented.

- The API for permissions should be getting clear.
- Retrieving current permissions works.
- Added API call /admin/create_test_data - intended to be used on an empty database to create some test data.
- Implemented creation of permissions, not tested.