refactor nway_other.cxx

refactor nway_other.cxx
In order to understand how the transitive and radial nway comparisons
worked I wanted to make the algorithms fit in a single window. I did
this by taking various types of initialization loops that were duplicated
between both algortihms and refactored them into seperate functions.
(mostly these common loops handled building paths that were between
our various iterators on each species lists of FLPs)

I thought it might be nice to turn the various functions I ripped out
into a class that manages the march of the iterators across the lists
of FLPs.

I also added some fairly basic unit tests for the nway (transitive) comparison.