Fix CI license check

Rewrote license check in python. Checks against a regex so that year number is irrelevant. Displays a diff if license is invalid. This runs in a default alpine docker base image with python, since nothing else is needed.

To make the CI run, I modified the setup_lcg89.sh script to not hard fail on Unkown OS. This is because that script is executed before all jobs.

Could this be a solution for the license check problem? This branch reports licenses are fine everywhere, I added another branch where I introduced a faulty license in a random file, so you can see the error output. Should I check more rigorously against false negatives?

What do you think?

@msmk @rlangenb