start refactoring GEO_Internals

Common/OpenFile.cpp

Geo/GModel.cpp

Geo/GModelCreateTopologyFromMesh.cpp

Geo/GModelFactory.cpp

Geo/GModelIO_GEO.cpp

Geo/GModelIO_GEO.h

Geo/Geo.cpp

Geo/Geo.h

Geo/discreteDiskFace.cpp

Geo/discreteEdge.cpp

Geo/discreteFace.cpp

Geo/discreteRegion.cpp

Parser/Gmsh.tab.cpp

Parser/Gmsh.y

Plugin/FaultZone.cpp