ENH: Sample Surface Mesh to Regular Grid Algorithm Improvements

[imikejackson]

I believe that we can substantially improve the algorithm/speed by the following:

Essentially use the "Slice Triangle Geometry" to create a 2D slice through the geometry at the Z Plane that is being worked on
Now use the 2D polygon shape to determine if a voxel is inside or outside of the mesh. This should go MUCH faster as we are only working on a 2D plane now instead of a 3D polyhedron.

There may be other improvements such as using the ray cast technique but casting parallel to the X axis, determining where the ray crosses the polygon, mark those voxels, and every voxel between those "hits" are either all in or all out side of the polygon.

[imikejackson]

This new implementation has resulted in a 100x speed improvement for the filter.

Further testing needs to be performed.