Add ability to configure columns on users per role report

We've got a sort of unique use case where admins who use our site want more info on users with a specific role. To this end, I've added the ability to configure which columns on the user table are visible for this report - with pass omitted, naturally - and to modify the table output accordingly. It even supports CSV export.

This could be made more configurable by changing the table renderer to use Views, and by making the view available to Features to modify. However, for a quick and dirty change, this should do the job, and since this module isn't maintained any more I figured I should just put it up in case anyone else needs it.