👌 Use notebooks for the examples

[s-weigand]

Using notebooks for the examples would allow us to:

• Have a rich text documentation of the case studies themself (e.g. explanation text and references to papers)
• Use read the docs to host a rendered version with plots

In order to achieve this, some extra tooling will be needed:

• [ ] Script to quickly convert notebooks to *.py files for debugging
• Distributed pre-evaluation of notebooks on the CI, so read the docs doesn't need to run them all at once (risk of timeout)
• Rewriting of the gh-action to use pytest + nbval papermill
• Compatibility of setup_case_study with notebooks since ipython doesn't define __file__

[jsnel]

In PR #103 the examples were ported to notebooks.