Add interoperability between pybind11 smtk python and vtkpython.

This commit teaches our pybind11 bindings how to deal with vtkpython objects. We can also "teach" vtkpython objects how to deal with pybind11 objects by subclassing the vtkpython object in python and adding free functions that are wrapped using pybind11 to the child python class (vktpython classes are not currently extensible). Also, an option to view the resulting mesh from the TriangulateFace operator has been added.