0022108: EDF 2547 SMESH: Duplicate elements only

1)
+  SMESH::SMESH_Group_ptr DoubleElements(SMESH::SMESH_IDSource_ptr theElements,
+                                        const char*               theGroupName)

2) set mesh to a filter
+  void prepareIdSource(SMESH::SMESH_IDSource_ptr theObject);