begin the world-owned wall tile rendering

also remove the health attribute on blocks, we'll instead store that
world-side
fix block flags, {Null, Stone, Copper, etc.} -> NullBlockType, etc.

tile renderer loads the wall type textures at the end of the 2d array tile
texture
change the primitive and wall tile lookup table to vectors

stuff the wall textures at the end of the main tile z texture,
intiialize all world-gen'ed non-null primitive tiles with a dirt wall tile