Additional plotting features for HWW couplings paper

Release notes

Various additional features added to TQHWWPlotter in order to make paper plots for HWW couplings analysis. Features include:

• plotting unit norm histograms in the subpad with an additional legend
• restricting range of x axis for main panel and ratio panel

Details

Instead of a ratio plot in the subpad, a function is added to TQHWWPlotter to take sig/bkg histograms from the main pad and plot them as normalised histograms in the sub pad, including with a legend. Also, tags are added to restrict the range of the x axis to user-defined boundaries.