Hierarchical clustering/dendrogram

[davidborland]

"The browser should have an automated classification feature in order to assess the level of heterogeneity. For example, in the Arora et al. data, there are three classes of cells based on CDK2 activity, but this is provided by the datasets themselves. It would be great if the browser were able to do this based on selected features (e.g. high versus low DNA damage) and then plot the different classes separately in order to look at different features."

[davidborland]

Implemented hierarchical clustering with dendrogram visualization.