[WIP] update to modern JupyterLab

[afshin]

trafficstars

I don't really know what I'm doing. But this is some amount of the way there.

I'd appreciate guidance (cc: @jasongrout @wolfv @martinRenou)

[afshin]

I took the output of the widget cookiecutter and patched in the logic from the old version.

I ran into one type mismatch (using unpack_models) which I handled with a kludge, but I imagine I have a version mismatch somewhere?

This is what I get right now:

[martinRenou]

This PR may fix it https://github.com/ipython/ipykernel/pull/1097 ?