0020968: EDF1545 SMESH: Problem in the creation of a mesh group on geometry

0020968: EDF1545 SMESH: Problem in the creation of a mesh group on geometry
  Correct a default _phySize

BLSURFPlugin_BLSURF.cxx
+    // GetDefaultPhySize() sometimes leads to computation failure
+    _phySize = mesh.GetShapeDiagonalSize() / _gen->GetBoundaryBoxSegmentation();

BLSURFPlugin_BLSURF.hxx
-    void SetParameters(const BLSURFPlugin_Hypothesis* hyp, blsurf_session_t *bls);
+    void SetParameters(const BLSURFPlugin_Hypothesis* hyp, blsurf_session_t *bls,SMESH_Mesh& aMesh);