Experiment with extending the QuadEdgeMesh

Instead of recalculating the quad edge mesh with each smooth level, involving lots of hash table insertions & lookups, I'm playing around with just extending the existing one.

So far the code looks promising, but I'll have to get it working and see how fast it runs.
Merge branch 'master' into qemesh-extension
Fix a few issues with QuadEdgeMesh extension, not working yet.
More QEMesh extension fixes, still not working.
Fix yet more issues.  Yet still not working.
More fixes.  Working?  Nope.
Debugging
Finally fixed the last stupid mistakes in the damn quad edge mesh extension.
Merge branch 'qemesh-extension'

Conflicts:
	subd.js
Add circle.obj