Big metavoxel update: removed unused pieces, converted heightfields to "spanners" in order to allow arbitrary transforms, switched to 16 bit heightfields with lossless compression, some rendering improvements.

You may have missed the parentheses here (or maybe I should have just folded the multiplication); green is multiplied by 31 and blue is multiplied by 31 * 31.  However, I like the idea of using values greater than 256; I'll use the ones you suggest.