Use double quotes as an alternative to escaping in values in meta ini files

Allow the following:

gridtype == Dune::UGGrid<2>, "Dune::YaspGrid<2, Dune::EquidistantCoordinates<double, 2> >"

instead of

gridtype == Dune::UGGrid<2>, Dune::YaspGrid<2\, Dune::EquidistantCoordinates<double\, 2> >