public class SubGraphRPermuter
Create all r-permutations of a graph given a set of $n>r$ vertex labels. This class should not be used to values of
$n$ that are very large!
This implementation depends on the classes UniqueSubGraphLabelings and PossibleSubGraphVertexSubsets.
These classes compute possible subsets of the vertices that might work, and orderings of the subgraph
that are unique, so in both cases, the total number of possibilities is hopefully reduced.
This class iterates through both of the lists (permutations and subsets), first over subsets, then over permutations
of that subset.