Spawn List Management

I'd like to move away from having the league spawn list being managed by a handful of admins on the BZFlag forums while this should be a league task, not a forum one. BZiON should take care of who will be able to spawn on the servers by communicating that information to League Overseer 2. In addition to league related things being in a single location, this will allow us to display certain information to players with "verified" accounts per se.

**Things To Do**
- Create the following BZiON permissions: `add_spawn`, `can_spawn`, `del_spawn`
- Create an interface for queued accounts to be added/removed to the spawn list
- The `add_spawn` and `del_spawn` perms will be needed for an admin to modify another player's account
- Create a "Stack Exchange"-like queue where an account would need the approval from 3 regular players (who have been players for longer than X time)
- This should mode should be configurable from `app/config.yml`
- Use these permissions to expose the following information:
- Servers, their status, and player list
- Servers where matches took place
- Communicate the `can_spawn` permission via League Overseer and accept `can_spawn` modifications from League Overseer (admins can add players to spawn list from in-game). This functionality will be exposed via the API and valid API credentials will need to be checked. (#46)