CRM-14856 - CRM_Profile_Form - Restore behavior of add_to_group_id wh

en there are multiple profiles

The behavior is to scan a combined list of UFFields, see if each UFField's
parent UFGroup has add_to_group, and use it if found.  If multiple
UFGroups define add_to_group, then the value of the last UFField wins.

I don't see this as good behavior -- just compatible behavior.