0020918: EDF 1447 SMESH: Mesh common borders

0020918: EDF 1447 SMESH: Mesh common borders
   Add means to notify CORBA API implementation level on group removal
   caused by hypotheses events (maybe in other mesh)

-  void RemoveGroup (const int theGroupID);
+  bool RemoveGroup (const int theGroupID);

+  struct TRmGroupCallUp
+  {
+    virtual void RemoveGroup (const int theGroupID)=0;
+    virtual ~TRmGroupCallUp() {}
+  };
+  void SetRemoveGroupCallUp( TRmGroupCallUp * upCaller );
+
+