(when a triangle can't find all three adjacent vertices: don't create new edge points, keep indices for old triangle. Still creates holes though, since vertex points are moved anyway.)

normal fix

some changes to Mesh entry handle

precompute new indexbuffer
- new vertexbuffer first contains vertex points in order of original vertices in vertex buffer
- new vertexbuffer then contains edge points that were created in order of edgeIndices

This will make it easier to iterate over all meshes in subdivide when we
want to add that feature.