- Improved balancing performance

- Added Fallback groups:
- groups of servers from which players will be sent to a defined balancing groups
- For example, SkyWars fallback group will contain all your skywars servers and all those players will be sent to your SkyWars lobby group when the game server is restarted
- Work in progress: add possibility to configure this fallback fro /lobby and /hub commands

BEFORE UPDATING TO THIS VERSION MAKE SURE YOU REGENERATE YOUR CONFIG, AS THIS VERSION IS COMPATIBLE WITH CONFIG VERSION 5 AND ABOVE ONLY