BUG: KuenSurface singularity at the pole
There is a singularity when v = 0. This patch checks for v = 0 and replaces it with a small number, .001.
This bug was noticed when running the VTK wiki example: Cxx/GeometricObjects/ParametricObjectsDemo2. While rotating the camera for the Kuen surface, the center of rotation appeared off. The z-coordinate was NAN for points when v == 0.
Also, the ordering of triangles was incorrect.