Get rid of the arbitrary bin/lib split and instead move as much as
possible into the bin crate, which becomes the main crate again.
The types and NBT handling are moved into separate crates, so they can
be reused by nbtdump and regiondump.
This reverts commit b53d34da3d.
With the change of the mipmapper data structure, we need a conversion
step anyways, so we can keep using the Vec before mipmapping.