Move vertex list build procedure to C level

[chrisk314]

Building the vertex list from the sphere and boundary geometry to provide as input to TetGen requires searching for and removing duplicate vertices. The current implementation makes uses of Python dictionaries and iteration in Python itself. This is probably the culprit for long run times when there are many vertices in the input.

Here it takes 52 seconds to build the vertex list for 1.7E6 points

MSP-Build  INFO     23-02-18 16:58:27.181  :    Building tetrahedral mesh
MSP-Build  INFO     23-02-18 16:58:27.183  :        -> building vertex list...
MSP-Build  INFO     23-02-18 16:59:19.368  :        -> calling TetGen (writing log to ./tet.log)
MSP-Build  INFO     23-02-18 17:04:28.108  :    Built mesh with 1688334 points, 7612699 tetrahedra, 16181955 faces, and 10257043 edges

Here it takes 16 minutes to build the vertex list for 6.8E6 points

MSP-Build  INFO     23-02-18 17:00:04.671  :    Building tetrahedral mesh
MSP-Build  INFO     23-02-18 17:00:04.678  :        -> building vertex list...
MSP-Build  INFO     23-02-18 17:16:36.952  :        -> calling TetGen (writing log to ./tet.log)
MSP-Build  INFO     23-02-18 17:38:19.653  :    Built mesh with 6766110 points, 35151505 tetrahedra, 72447292 faces, and 44061460 edges

Here it takes 24 minutes to build the vertex list for 21.7E6 points

MSP-Build  INFO     23-02-18 17:19:10.094  :    Building tetrahedral mesh
MSP-Build  INFO     23-02-18 17:19:10.123  :        -> building vertex list...
MSP-Build  INFO     23-02-18 17:43:49.512  :        -> calling TetGen (writing log to ./tet.log)
MSP-Build  INFO     23-02-18 18:55:39.583  :    Built mesh with 21659742 points, 108066844 tetrahedra, 224502984 faces, and 138094671 edges