HCluster find_root/find_parent review

[brifordwylie]

Right now the HClustering often generates long 'strings' of graphs where the depth of the graph is very deep and each level is only a binary split with just one/few node(s) joining in. This means the visualization is just a bunch of concentric circles. We need to review the find_root/find_parent logic to see if we can generate a flatter tree where sibling counts are higher.