[DONE] Groups and permissions refactor

[xoft]

What you're calling groups will be ranks in the new system.

The "player <-> rank <-> permissiongroups[]" has nothing to do with the config files, it is how the relations will be represented inside MCS: each player will be assigned to a single rank, and each rank will have several permissiongroups assigned to it. Nothing more.

The actual configuration will be in a database, probably four tables:
PlayerRanks:
- PlayerUUID
- PlayerName
- RankName (links with a Ranks record)
Ranks:
- RankName
- Prefix, Postfix, etc.
PermissionGroups:
- GroupName
- RankName (links with a Ranks record)
PermissionItem:
- GroupName (links with a PermissionGroups record)
- Permission