VanillaDisable

Partially redo configuration system (again):

• Move the worldgen config to the common command format, and add to common GUI (worldgen GUI still exists for pre-world creation GUI
• Move the gamerules that still exist in v3.x.x to the common command format
• Migrate the old configuration systems

Other substantial changes:

• Rewrite worldgen GUI (for pre-world creation) to be more user friendly

Code changes (that shouldn't affect the end user):

• Rewrite most of the config code (including the command) to simplify them and make development a lot easier (I now once again understand how my mod actually works!)