Changes

Add base stuff for a block with connected textures
Only adds "full", no horizontal or alike. All the models are done using
a Forge blockstate for simplicity, so copying the example Blockstate and
changing the textures is the easiest way to add a model
This is based off the tutorial by Darkhax linked below, though with a
few things modified to make it easier for extending and support adding
via EnumBlocks.
http://tutorials.darkhax.net/connected-block-textures.html