Quasi-final version of the "02a_base" tutorial

• Users management and recording of events is effective
• RGPD conformation
• More explanations, based on a "real-life" test
• Section on imbrication and chaining added

run() updates and proposes a list of tutorials

The run() function has been improved:

1. It checks for updates of the package before running tutorials
2. If no tutorial is provided, it proposes to select one in a list, and runs it

First release

Initial version of tutorials for module 2