Fix for the #21 note from issue 3134:

Fix for the #21 note from issue 3134:

- Import the flight_solid.brep from the SAMPLES of Salome.
- In SMESH, create a mesh with CADSurf
- In SHAPER, create a group of one face
- In SMESH, create the corresponding group on geometry
- In SHAPER, create another goup on another face
=> In SMESH, the mesh is notified that the shape has changed. I have to compute the mesh again to create a new group.