Update the worldpacker project for 1.16.

Finished this off yesterday just forgot to close it.

PresetPacker is basically complete, but should be tested for usability. The preset versioning in particular might need some tweaking, but that requires some preset dev feedback first.

Forge allows modders to package json files in the mod's resources folder, which are automatically packaged as the mod's datapack and included when worlds are created. Should make users aware that this is a feature of presetpacker.