Enhancement of plot helper methods and error messages

What does this MR do?

This MR improves the PlotHelper in the following ways:

• set_limits now allows dict-type arguments and min and max, which consult the data for minimum and maximum values
• set_scale is renamed to set_scales to be more consistent with the other helper names
• The PlotHelper now generates more helpful error messages, including the values given to the plot helper and the docstring.

Can this MR be accepted?

• Implemented the enhancements
• Tests added or adjusted
• Full test coverage
• Pipeline passes
• Changelog entry added
• Version bumped

Anything to double-check?

Nope.