replace itkwidgets viewer in jupyter notebooks with pyvista viewer

[cchriste]

Lots of info in #1168, including the underlying reason for this: crashes most likely due to python module linking issues.

Note that the pyvista can do anything vtk can do. It's just built on vtk with a more comprehensible interface (kind of like ShapeWorks on itk). It's classes are just wrappers around vtk classes. For example, adding a volume to a plotter returns the vtk.vtkVolume, and all functions (help(vtk.vtkVolume)) are available.
If we put our heads together I'm sure we can figure this out.

Note also that itkwidgets's viewer is built on vtk, so look for def view(... in here if you want to try to emulate it more closely.

[sheryjoe]

@jadie1 @iyerkrithika21 you will take the lead on this as you restructure the notebooks.