More layering fixes

- Call RecalculateBounds on layer-objects once their verts are set.
Otherwise the depth-sorting for transparent geometry goes bat-shit.
- Don't bother rebuilding GeometryFactory geometry on Start(). Doing so
undoes layers, which was probably causing all sorts of horror.
GeometryFactory should be an editor-only class, really.
- MeshInfo class and editor added. This just dumps a list of verts in a
mesh. Added to help me debug the layers and spot the above issue.
- House floor 1 lives again!