Skin Layers 3D

Bugfix release. Changes:

- Head voxel size gets scaled from the middle of the head, not from the bottom

- Centered the layers on PlayerHeads better

- Reworked the skin texture logic. This prevents crashes with HD skins(they will just render in 2d), adds support for resource pack skins and probably improves compatibility with other mods.

- Fixed layers getting rendered when in spectator while having 3d layers disabled

- Fixed First Person left-hand sleeve being at the wrong location

Also, note the license switch away from MIT! Get into contact if you need more permissions than granted by the license!