add ability to filter by screened or final labels on upset plot

[TNRiley]

Add an argument to the upset plot that allows the user to select label values (eg. screened, final). Label metadata would either be added to the data.

We could either add cite_label to the output of compare_sources, or at least give it an argument to add the label. This idea may extend nicely to the heatmaps as well, where you can see the overlap of the screened or final datasets as well.