Reports/Query people who are only co-authors on IPs
current co-authors query returns people who are also submitters of other IPs, or SS contributors or submitters. that makes it hard to calculate to how many co-authors we could offer a place to register, as some are registered already. Could we generate a listing of those woh have no other role in the conference (on frab) than being named as co-authors (i.e. have not user accounts yet)?