Added initial framework for shulker-based palettes

[Firigion]

The thing is still missing support for set_block to use palettes, but that's independant of the current development. It should be compatible with the comand-based palettes WE style. There's even a command to register palettes from command line that should work fine if the argument type '' returns a map like we talked earlier.

The way it works right now is that calling /world edit palette make holding a shulker box will map the blocks into a palette by counting how many slots each block has assigned. I like this better than counting stack counts for two reasons, but it's up for debate:

1. It's more visual, easier to estimate how a palette will look
2. It allows to encode other info into the stack size. Right now, stacking now layers or sea pickles defines how many of those it's gonna put in one block.

It uses an alias system for stuff that can't be obtained in item form (liquids, portals, air), or items that don't correspondo to the block (crops, seeds, rs dust).

I'm not sure how the syntax for set commands should be with registered palettes. Maybe to avoid conflicting commands with blocks i'd do something like /world-edit set frompalette <index>, but I wanna hear your opinions.

PS: I don't know how to spell.

[Ghoulboy78]

oh wow, this pr is so old it modifies world-edit.sc... Might it be best just to delete and then re-do these changes on a new, up-to-date branch?