make-plots: Let RatioPlot find refdata from inputdata

For me this makes it easier to normalize a RatioPlot to a prediction instead of the data (cf. image). Instead of having to specify the data set (dDD-xXX-yYY) for each plot I can just pass the RatioPlotReference=/.../file.yoda/THE_ANALYSIS and let it use the default weight from that yoda file for each data set of given analysis. Maybe something else exists to achieve that, but this seems quite intuitive and easy to me.