bump min client version and idom-jupyter

bump to 0.7.3

avoid multiprocessing + actually set the import source URL

cannot pickle lambda

misc fixes

- Make server extension authenticated
- Try to determine if running with adjacent notebook server,
  and if not, spawn static file server from which to provide
  web modules. This will probably just be used by VSCode.
- rename _jupyter_server_base_url to _import_source_base_url
  to better indicate that this is a manually specified
  location where web modules are served rather than a jupyter
  server (though it might be).
- bump model and view versions for everything.

update yarn.lock

update yarn.lock

bumpy idom version + bump idom-jupyter version

misc minor improvements too

bump version for license file