#13 Improve the space subdivision algorithm in MG2

[Marcus Geelnard]

The space subdivision algorithm in MG2 is not really optimized. A qualitative and quantitative improvement should be done.

One simple requirement: the algorithm should essentially produce the same raw/compressed data for meshes that are the same except for their scale (so for instance a bunny with the unit inches should produce the same data as a bunny with the unit meters - only the bounding box information should change).