Group Member Bulk Add (via UI)

We can provide the ability to bulk add group members via the COmanage UI using one or more of the following approaches:

1. Within a group membership listing, provide a "bulk add" action near the "Add member" form that lets a group owner drop in plain text identifiers, allow the group owner to select more than one Person at a time using the person picker, or both.

1. From the My Population listing, allow an admin to refine a filtered listing of CO People and then select an "Add to group" action or "Create group from listing"

Both approaches - adding members from the Group Member listing and the My Population listing - will make membership addition faster. Approaches will be broken into subtasks on this ticket.