Resolve "code cleanup of the plotter"

This is not the fully cleaned-up version yet, but all the (expected) changes to the output files are in now, such that it seems more useful to make a new branch to work on the code cleanup that should not change the outputs.

Release Notes

Only very few changes to the usage have emerged from te cleanup:

• The former tag style.legendHeight is now called geometry.legend.height to increase consistency.
• If several signal samples are added to a plot with a sub-plot, the drawing order in the sub-plot is now consistent with the drawing order in the main canvas (which it was not before).

For all the differences, check summary.pdf