Consider replacing JCommander with picocli for the CLI part

[AuPath]

picocli offers several improvements over JCommander:

• Automatic documentation generation (man page, html ...).
• Easier to unit test the CLI itself. We had some problems in the past related to this.
• Applications built with picocli can be natively compiled with GraalVm native images. We do not strictly need this but it is interesting.

@marioscrock, what do you think?

[marioscrock]

Agree! I chose JCommander because it was the recommended and easier library many years ago, picocli seems a good alternative with a very active community (link) and I like that it supports native compilation.