Custom logging instead of python's print()

Created by: lkugler

There was a suggestion to replace python's print with more elaborate logging so that you can turn off / on more or less output.

My opinion is that there should be as much as necessary of print to a log file in order to determine later whether there was a mistake or where a mistake came from. The amount of print should not be reduced "just" to remove unwanted distraction on the screen.