0022104: EDF 2550 SMESH: 2D viscous layer, allow specifying edges with viscous layer

0022104: EDF 2550 SMESH: 2D viscous layer, allow specifying edges with viscous layer

In addition to implementing IMP, avoid "limiting" _thickness to zero:

-    _thickness = Min( _hyp->GetTotalThickness(), maxPossibleThick );
+    if ( maxPossibleThick > 0. )
+      _thickness = Min( _hyp->GetTotalThickness(), maxPossibleThick );