Add further customisation options for which orbital graphs are returned

[wilfwilson]

For a given set of points that the group acts on (which will give the vertices of the graphs), and for a given subset set of points from which to pick base-pairs...

• Return absolutely all orbital graphs (i.e. including orbital graphs with loops)
• Return all non-loop orbital graphs (i.e. excluding orbital graphs with loops)
• Return all-but-one non-loop orbital graphs (in particular, don't construct and return one of the orbital graphs with the maximum number of edges)
• Return all orbital graphs that have at most k edges, for some k
• Return all non-futile orbital graphs
• Return only orbital graphs where the base pair comes from the same orbit
• Don't return orbital graphs with base pairs from distinct equivalent orbits.
• ...and various combinations of these things.

Perhaps there are other clever ways of proving that you don’t have to use some orbital graphs, for your particular purpose, and so you shouldn't need to create them in this case.

This follows a conversation with @ChrisJefferson and @Munsee.