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.

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.

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