* Replace use of local table with compostability values with a call to
`minetest.get_item_group()`.
* Define local alias for `minetest.get_item_group`.
* Remove the now unused static compostabilty values table.
Implements a composter block with crafting recipe, and some more
uncraftable blocks representing various stages of filling.
Adds a list of items that can be used with the composter and the chances
of these items adding a layer to the composter.
Implements methods to add compostable items to the composter, to update
the composter to various levels of compost and to harvest an item of
bone meal when the composter is ready.
Textures were taken from XSSheep/Nova_Wostra Pixel Perfection texture
pack.
kabou
MysticTempest