Refactor a bit the way Docker images are used; the third party warnings are now a full-fledged demo.

Installation: simplify and use a Yaml file. Jupter-lab has been considered and discarded as it introduces many issues (table of contents is not working, currently up-to-date extensions are not compatible with up-to-date jupyter lab and so forth...).

Updating and cleaning-up introduction and procedural programming part. The section introducing pointers and references has been refactored a bit.

Exercices about templates have been refactored (and greatly reduced: all the error handling will be tacked in the next notebook).

Introduce CMake files that will be included in each of the TPs to avoid repeating endlessly the same configuration steps.

Revamp the TP for procedural programming:  make it clearer, add one session and put some exercices in a later one to avoid a heavy block with more then 10 exercices at once. Solutions have been rewritten to be generally more elegant; I have also renounced to separate declaration and definition as this was definitely a pain for most participants the first day.