Groups: Need new attribute: Locked/Unlocked

Parent groups should be lockable so that users can not be added to the group. Locked groups would not show up when editing user records, but would show in the group drop down on the Find Contacts page.

The system allows hierarchical groups. Administrators should be able to make parent groups containers for other groups only, with no users in the container groups.

If you create a separate Profile for different kinds of events, where each Profile is configured to add new users to a particular group, then you can quickly search for all participants of certain event classes by creating a group that corresponds to each profile (event class) and then making those groups have a common parent group. By locking the parent, users editing user records cannot place users into the parent container group, but can search on the parent group to find all participants of all events of the same (logical) event class.