22580: EDF 8049 SMESH: Problems with viscous layer

+ some fixes for ~/salome/Files/Studies_FROM_BUGS/VL_Usecase2.hdf

  1) Prevent negative volumes caused by smooth on curvature
  2) Add EDGEs to smooth in updateNormals()
  3) Fix too high _stepSize causing failure of smoothing on FACEs
  4) Correct finding EDGEs needing smooth
  5) Fix AddShapeToSmooth(), FindIntersection(), updateNormals(), SegTriaInter()