Create single cell data demo

[cmdcolin]

Examples of this could include making an example of a multibigwig for single cell or something like this

[carolinebridge]

Some ideas from Lincoln for compatibility / best usability with single cell data:

• UMAP plugin that shows clusters or single points of data, whereupon clicking it can show the corresponding wiggle track
• look at expression levels of a series of isoforms, isoform specific differences between cell types
• compare two different clusters of single cell data, each cluster becomes a track and the track shows you the known gene isoforms and then the short read sequence or the distribution of short read seq from that cluster
• integrate SEURAT formatted objects and dump into a UMAP in a relatively portable way