InfdevOldWorld now allocates Blocks as a 16-bit array and reads Add into the top 8 bits if present. MCSchematic also allocates Blocks as uint16 and uses WorldEdit's extension to the schematic format to store the Add arrays.
Conflicts:
test/extended_id_test.py
Add a function to ChunkBase for getting the slices for a chunk's arrays and the area of the chunk bounded by a given BoundingBox
Remove copyBlocksFromFinite and use copyBlocksFromInfinite as the default implementation
Rewrite copyBlocksFrom to use chunk.getChunkSlicesForBox instead of world.getChunkSlices
