Node insertion, precursor to segmentation.

Lines 367 to 377 handle node insertion.  Tested locally by enumerating around added node and all adjacent nodes, enumerating regions around nodes, and running the knn W builder.  The later hit the new node many times and did not fail to generate a W.

Now that this in, it is possible to densify the edge by adding nodes.  
ToDo: Add the segmentation code.