Refactored the code to use default "common" dyes
rather than directly from flowers.

This mod now depends on "default" and "dye" from the Minetest common
sub-game.  Since the default dye mod uses default flowers, this mod no
longer checks for what version of flowers you're using, or even depends
on it.

Bottle-based textures have been replaced with piles of dye powder, based
on the default red dye texture.

All dyes are obtained by crafting, not cooking, for consistency with the
default dye mod.

The somewhat-complicated method using separate "pigment" powders, glass
bottles and "liquid dye base" has been done away with.  Now it's just
dry dye powders, as with the default dye mod.

Also, got rid of the whole paint scheme, in favor of dry powders.

All old dyes, paints, and Unified Dyes pigment powders have been aliased
back to the standard dye powders.