supertree via ranked trees on a taxo scaffold

This page describes an alternative supertree method summarized by:

1. taxonomic groups that are not contested by any input must be in the final supertree,
2. after honoring that constraint, we attempt to find supertree which maximizes the "max weight of input tree edges displayed" objective function using tree-based ranks to supply the weights.

This doc builds off of the supertrees using tree ranking doc; so that is considered background reading.