Add Stacked Bar Chart for Generic Assay to Oncoprint

[inodb]

Currently generic assay is only displayed as a heatmap. See e.g. for single cell fractions per sample it currently looks like this:

See link

Note that the mutational spectrum track is shown as a stacked bar chart and we could show the cell fractions in a similar manner. We could e.g. change this menu:

To say "Show as stacked barchart". Then the relative counts would become a single track of stacked cell types