[spaces.rt] add RaviartThomasSpace to provider

dune/gdt/spaces/rt.hh

@@ -14,6 +14,7 @@
 #include <dune/xt/grid/gridprovider/provider.hh>
 
 #include "rt/interface.hh"
+#include "rt/default.hh"
 #include "rt/dune-pdelab-wrapper.hh"
 #include <dune/gdt/playground/spaces/block.hh>
 
@@ -52,6 +53,14 @@ private:
     typedef GDT::DunePdelabRtSpaceWrapper<GridLayerType, p, R, r, rC> Type;
   };
 
+  template <class G, int p, class R, size_t r, size_t rC>
+  struct SpaceChooser<G, p, R, r, rC, GDT::Backends::gdt>
+  {
+    static_assert(rC == 1, "");
+    static_assert(r == G::dimension, "");
+    typedef GDT::RaviartThomasSpace<GridLayerType, p, R> Type;
+  };
+
 public:
   typedef typename SpaceChooser<GridType, polOrder, RangeFieldType, dimRange, dimRangeCols, backend_type>::Type Type;
   typedef Type type;