More plastering

Plaster can now cover multiple block types using metadata, and only
takes up one block id. Up to fifteen different types can be set to
plasterable, in the PlasterBlock class. There's an array in getPlasterID
and getBlockIdFromPlasterID (that must match exactly) that stores the
plasterable block IDs.
Merge remote-tracking branch 'origin/master' into Matt's-Branch
Textures

Changed textures so that marble is brighter and whiter and limestone is
more yellowed, since before it was the opposite.