The main function for the admin member interface.

• Accessed from the "View/Delete Members" item on the admin menu
• Allows viewing and deleting of all members
• Called by action=viewmembers or action=viewmembers;sa=all
• Displays a sortable list of members in the admin center
• Handles the admin member-search interface
• Requires the manage_members permission
• Sub-actions:
• all - the main member list (default)
• delete - used when deleting members (requires valid session ID and profile_remove_any permission)
• query - called by member-search form to search for members
• search - loads the main member-search interface