Load mob spawners and NBT lists more cleanly (fixes #135).
Recount non-air after chunk generation (fixes #239).
Added block placement handling for several blocks (see #119).

Handling for stairs, chests, ender chests, slabs, hay, logs, and quartz.
Improved canAbsorb and added canOverride, implemented for slab, fire, and tall grass.
Made warning on incorrect MaterialData more uniform, improved formatting.