Switched from a virtual function implementation to a template system. It seems...

Switched from a virtual function implementation to a template system. It seems to be faster. I still need to fix up the container_poly part, as it's a mess right now.

git-svn-id: https://code.lbl.gov/svn/voro/trunk@42 6221c96e-593b-4ce1-a500-64c4038a1943