On the role assign page, list who is assigned the role for roles with only a few assignments

This was something our administration staff asked for. When you want to check who is assigned to a number of different roles, the current interface is a pain. You have to visit lots of pages.

A simple solution was to edit the role assign page, so that for roles with between 1 and 10 role assignments, it adds a list of uses to the table. (Being an OU admin requirement, they want usernames there too. Naturally I would not display them in core Moodle.)

Do we want this in 1.9?