The 'histogram' method on SequenceableCollection added by Roassal2 fails due to
xScale/yScale not being implemented on RTHistogramSet.
I added implementations of both as:
^ RTLinearTransformation instance.
to RTHistogramSet which at least gets a histogram working. I'm not sure what the
proper fix actually is. I thought maybe adding this implementation on RTAbstractDataset
would be the right thing to do...