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.
Fix disconnect when sending empty chunks
Fix whitespace
Included a copy of the GPL in the distribution (fixes #147).
Limit player yaw to values in the [0,360). Fixes #173.
Added .gitattributes to enforce LF line endings.
Fixed skylight in empty ChunkSnapshot sections to be 15 instead of 0.

Also, fixed logic for isSectionEmpty.
Added missing Override annotations, fixed GlowWorld and GlowPlayer line endings.
Fixed loading of blocks with high IDs.
Merge branch 'chunksending'

This merges changes from pull request https://github.com/GlowstoneMC/Glowstone/pull/247.