added a hook for derived class needing to monitor instance changes
added a hook for derived class needing to monitor instance changes


ProjectPersephone/Orekit,wardev/orekit,liscju/Orekit,petrushy/Orekit,attatrol/Orekit,ProjectPersephone/Orekit,liscju/Orekit,Yakushima/Orekit,Yakushima/Orekit,CS-SI/Orekit,petrushy/Orekit,treeform/orekit,CS-SI/Orekit,attatrol/Orekit