Reduce amount of whitespace for "high" figures

Originally mentioned in #309 (closed) decided to create a seperate issue for it.

added Enhancement Scheduling Scheduling GUI labels

changed the description

I think that one should rework the whole plot generation such that the items in a plot (schedule or resource) has a well-defined height, that can be specified and then the figure size adapts. This, sort of, happens for schedules now, but not in a very exact way. I think the main problem is that the margins are relative to the figure size in Matplotlib, so one will have to adjust them as well.