Send ndarray chunk format
Merge branch 'master' into ndarray
Alternating ore checkerboard on surface for testing chunks
Internally generate with ndarray
Convert populators to use ndarray; restore normal grassy landscape
Merge branch 'ndarray'. Closes GH-12

Requires deathcap/voxel@99311775d4e5576cbb2fdabdcb0928ba8a8d3455