23269: Meshing a composite block with IJK

23269: Meshing a composite block with IJK
  StdMeshers_CompositeHexa_3D.cxx

And more:

1) Avoid creating actors for not shown mesh objects
  SMESHGUI_ComputeDlg.cxx

2) Add wait-cursor while group deletion, which can be long on large meshes
  SMESHGUI_DeleteGroupDlg.cxx

3) Avoid getting elem types of a new group on filter, which can be long
  SMESH_Gen_i_1.cxx