changed tox.ini to run notebooks from the tox envdir (.tox/notebooks) so they don't overwrite those in your local copy.  Updated the notebooks to load env files from the package mechanism importlib_resources.  This now gets them from the copy of env_data down in the tox python virtualenv.

adding notebook-list, a list of notebooks to *include* in run-all-notebooks (already modified in last commit).  This is so you can run tox without it choking on your local broken notebooks in development :)

made the env loading more forgiving (in persistence) to allow the loading of old envs, and msgpack files with .pkl extension.  Also give default 100 max_episode_steps where this is missing.  Add test-saved-envs notebook to test loading all old envs.

Updated test for generators to check that distance map is not recomputed when loaded correctly

removed prints for debugging.
updated notebooks to new rendering code --> Tests should pass

removed prints for debugging.
updated notebooks to new rendering code

removed prints for debugging