Added "litebans.override" permission - without this permission, players cannot override previous bans/mutes. This prevents unbanning a player by banning them for 1 second, for example.

Fixed previous IP bans not being overridden by new IP bans. Regular bans still cannot override IP bans.

1.8.3: Also allowed players with the permission "litebans.unban" to override previous bans.

1.8.4: Fixed bug where login threads would get stuck in rare cases.