add taxonomic-vs-phylogenetic distinction to induced_subtree

[arlin]

The main synthetic-tree view uses dotted lines for edges supported only by taxonomy.

Add an option to induced_subtree to support returning the relevant information, so that clients can distinguish taxonomic and phylogenetic parts of the tree.

Complications

1. Currently induced_subtree returns Newick so it is impossible to put this in the tree. However, if there were a nexson or arguson option, this could include a designation for each edge. Alternatively, without a new format, phyloreferences could be used in the manner suggested in link supporting_studies ids to supported nodes in induced_subtree #125.
2. This will require a method for assigning the status of an induced edge collapsed from a series of original edges in the full synth tree.