Overhaul of the set up required to be able to run the formation

@steff @vrouvrea

This merge request deals with #25 (closed), #36 (closed) and #35 (closed).

By far most of the modifications are from #35 (closed), and to be honest some of them are not clean enough, but I really needed to have a functional set up to be able to review and edit the notebooks (the main issue with Podman was to ensure that modifications done on the notebook in the browser may be saved correctly in the notebook file on the host).

Tbh, I wonder if we shouldn't move away from Jupyter notebooks in the future and use a Web-based solution (as the "Run this code" in https://en.cppreference.com). But this is a discussion for another time

Due to the modifications I had to do, I would like both your approval before merging it. Thanks!