Called by BaseObjectHandler for addElement(),
when there is a new BaseObject instance which has been created by BaseObjectHandler,
and which has to be added to the collection property.
This method has to be invoked just after the creation of a GroupIDImpl,
to register the current ACSTreeBaseListenerImpls as listeners of any change
among the GroupID members.
Called by DialogBox.showExplorerSelectionDialog() for actionPerformed(),
when the property is a Collection, a Map or an array,
and the property type is a BaseObject
which has to be selected in the explorer through the button 'Select'.
Called by handleSelectionDialog() for actionPerformed() and directly by
actionPerformed() for restricted values, when the property is a Collection,
a Map or an array, and the property type is a BaseObject
which has to be selected in the explorer through the button 'Select'.
Check if there is at most one DisplayableLink which has all of
its AccessControlLinks with a strengthen relation (OWNER, HAS_MEMBER,
HAS_CHILD, IS_ALIAS, RUN_UNDER).