on user update/create/delete

for updates and deleted, we check to see if the requestor has permission
to update users in the exising users group (as it exists in the database)

for all actions, we check to make sure the requestor has permission
to put users into the requested group

git-svn-id: svn://svn.open-ils.org/ILS/trunk@6017 dcc99617-32d9-48b4-a31d-7c20da2025e4