Add a way to promote people to "map co-owners"

[Narwhale]

Co-owners would have the ability to download and change flags/lock maps and possibly add and remove other players from the map. Co-owners won't be able to delete the map, change backups or remove the original owner from the world. The command would be something like /add [username] -o.

[itsmiiolly]

I'll have a crack at this.

[Electroid]

Manager system