0051789: TC7.2.0: NoteBook cannot update study

0051789: TC7.2.0: NoteBook cannot update study

Fix approach to storage of NoteBook variables.
Before the fix: names of variables are stored in PythonDump commands
and nothing is stored in the Study.
Problem: after variable removal, the PythonDump script becomes invalid.
Fix: names of variables are stored in the Study, PythonDump commands
store indices of variables within "StringAttribute".

class SMESH_Gen_i {
...
-  void UpdateParameters(/*CORBA::Object_ptr theObject,*/ const char* theParameters);
+  void UpdateParameters(CORBA::Object_ptr theObject, const char* theParameters);

+  const std::vector< int >&  GetLastParamIndices() const;
+  std::vector< std::string > GetAllParameters(const std::string& theObjectEntry) const;