* @param id the unique if of this entry
*/
public DockableHandle( Dockable dockable, String id ){
this.dockable = dockable;
this.id = id;
source = new MultiDockActionSource( new LocationHint( LocationHint.ACTION_GUARD, LocationHint.RIGHT ) );
properties = new HashMap<Path, H>();
history = new LinkedList<Path>();
}