Improve discoverability of subgroups indication in /groups listing (harder, but better fix)

Currently the way you find subgroups of a parent is to click the number of subgroups in the /groups listing. The only interface is to click the number following "Subgroups", which is pretty non-obvious.

There should be a hierarchical view. This is a hard problem, and has been discussed - with no good technical solution.

Despite the fact that it's hard, this does not remove the need for some kind of improved interface.