identify super structure in an mc cover, based on hcluster of the confusion matrix

mcell_mc_hierarchy(mc_id, mc_hc, T_gap)

Arguments

mc_id: id of metacell object ina scdb
mc_hc: hclust object onthe metacells (e.g. derive from mcell_mc_hclust_confu)
T_gap: the minimal branch length for defining a supper metacell structure