More work on 0.4.0
* Changes to localization/customization of Strings:
  - Ability to choose to use the header, or not
  - Ability to set a String to "" (empty) to prevent it from being sent (/!\ not compatible with all Strings, only those who support multiple lines)
* Refactored Messages config handling: centralized more things in Core
* World: Linked additional Worlds to additional sub-worlds (End/Nether). Tested and working. Fixed a lot of bugs.
* Cuboid: Fixed a bug in Farm flag
* General:
  - Reworked AFK command
  - Reworked FlySpeed command
  - Added WalkSpeed command
  - Added Time command
  - Added Weather command
* Player: implemented kick, ban, banip and mute commands. All of them handles both permanent and temporary punishment.
* Fixed a lot of bugs in various stuff