number collapsing algorithms

This has come up before, but we never did anything about it.

I think we probably need a way to set a global option for collapsing
page number ranges. The one I used in my code is the Chicago version,
which I imagine would work for most cases. But I could imagine there
may be others.

Discussed previously here in this thread:

One problem: we don’t really have a way to set a global option.

Any thoughts on dealing with this?