Added: Biomes are now exported into schematic files.

Biomes array is indexed z, x

When importing, biomes are only copied on request.
Added: idStr in materials.yaml is now minecraft's internal name for each block.

This name is used for unstitched texture files so we'll be needing it soon.
materials.idStr now maps block IDs to idStr.

idStr is not unique now and was never used by MCEdit before.