Incorporate clustering uncertainties

[tanghaibao]

Based on Jingping's idea below:

Since the program takes an existed tree and that tree construction itself can be fishy sometimes. I wonder if the algo might also try to consider alternative tree shapes to improve cutting. Search of tree shape itself is NP-hard problem, but some simplified thing might be doable. For example, the algo could take not only the tree shape but also node support for the input tree. Then for nodes whose support is low the algo could try to switch around its "children". For example in the figure attached, say if the support for node N4 is low, the algo could try the alternative clustering shown in the right part of the figure, which in this case might narrow done the defining of the group (from 130, 150, 90 to 130, 150). I assume in some other cases this could result in expansion of group definition too.