Jupyter data-widget based on VTK sources

A typical installation requires the following commands to be run:

pip install vtkdatawidgets

Or, if you use jupyterlab:

pip install vtkdatawidgets

If you are using notebook less than version 5.3, you will probably also need to run:

jupyter nbextension enable --py [--sys-prefix|--user|--system] vtkdatawidgets

, or

jupyter labextension install @jupyter-widgets/jupyterlab-manager

, as appropriate.