[Fix] Fixed the NPE when leaving the server if no hub has been set.
[Fix] Fixed join and quit messages when not switching a world
[Fix] Fixed a save bug when leaving the server.
[Fix] Fixed a lot of bugs refering to the registerer system.
[Optimize] Optimized a lot the loading / saving method for player statistics
[Add] Added linked-worlds feature
[Add] Added the enderchest separator
[Add] Added new commands to manage the worlds.yml in game without having the risk of corrupting the file when manually editing it.