Resolve "systematics breakdown/impact plots do not exhibit sign flips"

Release notes

Breakdowns and Impacts now have correct sign treatment implemented. The ActionPlotResults supports plotting the negative and positive uncertainty component with "style.fillColor.neg" and "style.fillColor.pos"

Details

Older results files might not be usable anymore, as the error symmetrization was dropped in favour of a correct sign treatment. Older Breakdowns thus will both positive and negative error displayed on the same side of the graph.

Closes #65 (closed)