Eventdisplay code maintenance

[GernotMaier]

This is a very general cleanup and code maintenance step for the Eventdisplay related step:

• improved printout of help messages
• improved (but still incomplete) commenting
• code style and readability (PEP) of all Eventdisplay related files (using black

I am completely aware that this is a little bit of a pain to merge, but having some consistent code format is important for long-term maintainability.