Add permissions to Referees Administrator role

[troccoli]

We already have a role called Referees Administrator but it doesn't have any permissions.

A Referees Administrator can do anything the Site Administrator can do with seasons, competitions, divisions and fixtures. They can not however do anything with clubs, teams or venues.

• update all policies to account for this role (and make sure we have tests for this)
• update the API to account for this role (and make sure we have tests for this)
• update the frontend to account for this role (and make sure we have tests for this). It may be worth it to do this bit after Refactor the dashboard to work with different roles #126