World Preset Manager

Started this as a need from Bacon Donut to create superflat presets for worlds to give modpack makers the capacity to ship world types.

This is how it works, it lets you edit the mod config file to define settings for one or more superflat presets, and these will be added to the World Type selection button in the create new world menu, so that a modpack creator can predefine these presets for the world and the final user can just choose that without having to tweak settings.