Define GOCAD as standard input for workflow

Ask ERCOSPLAN to provide GoCAD files instead of AutoCAD files. If GoCAD TSurf data is provided, the GocadTSurfaceReader command line tool could be used to convert the theoriginal file intonvtu files containing on triangulated 2D surface each (effectively skipping GINA, OGS2VTK, and ExtractMaterials in the list above (copied from @rinkk )