DARK - Makes group unseeable (default)
QUELL - Kryponite (prevents wizardly meddling)
STICKY - Makes group permanent (temporary is default)
TATTLE - Notify owner when members enter/leave the group.
COPY - Turns a normal object into a copy-object "group".
OWNER-GROUP - This group owns things. Owner-Group is automatically
@set when something is @chowned to the group, and
@reset when group is @toaded or @purged.
LINK_OK - Permits owner-group members to chown things to it.