0022098: EDF 2036 SMESH: Create groups from none conected parts of a mesh

Move SMESH_ElementSearcher to from SMESH/SMESH_MeshEditor.hxx SMESHUtils/SMESH_MeshAlgos.hxx
in order to make SMESH_ElementSearcher accessible from Controls/SMESH_Controls.cxx

-  static bool FaceNormal(const SMDS_MeshElement* F, gp_XYZ& normal, bool normalized=true);
-  static std::vector< const SMDS_MeshNode*> GetCommonNodes(const SMDS_MeshElement* e1,
-                                                           const SMDS_MeshElement* e2);