added legacy interfaces to Legacy namespace

FileIO/Legacy/MeshIO.cpp

FileIO/Legacy/MeshIO.h

FileIO/Legacy/OGSIOVer4.cpp

FileIO/Legacy/OGSIOVer4.h

FileIO/XmlIO/Qt/XmlGspInterface.cpp

FileIO/readMeshFromFile.cpp

Gui/DataView/MshView.cpp

Gui/mainwindow.cpp

SimpleTests/MeshTests/CollapseMeshNodes.cpp

SimpleTests/MeshTests/MeshSearchTest.cpp

Utils/FileConverter/GMSH2OGS.cpp

Utils/FileConverter/VTK2OGS.cpp

Utils/MeshEdit/moveMeshNodes.cpp

Utils/MeshEdit/removeMeshElements.cpp

Utils/MeshEdit/removeMeshNodes.cpp

...pleMeshCreation/createMeshElemPropertiesFromASCRaster.cpp

Utils/SimpleMeshCreation/generateStructuredQuadMesh.cpp