Hold off GUI creation, and use Jupyterlab Dashboards when they land

[SimonBiggs]

It might still be quite some time before it is available, but I think using the following tool to build our GUIs would be ideal:

jupyterlab/jupyterlab#1640 (comment)

That way, the best thing for the GUI side of things is stay compatible with Jupyterlab, build mini Jupyterlab widgets for our library using tools like https://github.com/InsightSoftwareConsortium/itk-jupyter-widgets/blob/master/README.rst

And then, once we have a collection of Jupyter widgets, when dashboarding lands, we have ready made GUI creation.

[SimonBiggs]

This is a helpful reference. ITK widgets will likely be very helpful in the future. So too will Jupyter dashboarding. Will close this and will re-address these when these features land.