[space] added needs_grid_view

* this can be used with space.tools to automatically create an appropriate
  grid view or part, as needed for each space

dune/gdt/space/continuouslagrange/fem-localfunctions.hh

@@ -96,6 +96,7 @@ public:
   typedef BaseFunctionSet::FemLocalfunctionsWrapper<BaseFunctionSetMapType, DomainFieldType, dimDomain, RangeFieldType,
                                                     dimRange, dimRangeCols> BaseFunctionSetType;
   typedef typename BaseFunctionSetType::EntityType EntityType;
+  static const bool needs_grid_view = false;
 
 private:
   template <class G, int p, class R, int r, int rC>

dune/gdt/space/continuouslagrange/fem.hh

@@ -68,6 +68,7 @@ public:
   typedef typename GridPartType::template Codim<0>::EntityType EntityType;
   typedef BaseFunctionSet::FemWrapper<typename BackendType::BaseFunctionSetType, EntityType, DomainFieldType, dimDomain,
                                       RangeFieldType, dimRange, dimRangeCols> BaseFunctionSetType;
+  static const bool needs_grid_view = false;
 }; // class SpaceWrappedFemContinuousLagrangeTraits
 
 

dune/gdt/space/continuouslagrange/pdelab.hh

@@ -93,6 +93,7 @@ public:
   typedef typename GridViewType::template Codim<0>::Entity EntityType;
   typedef BaseFunctionSet::PdelabWrapper<BackendType, EntityType, DomainFieldType, dimDomain, RangeFieldType, dimRange,
                                          dimRangeCols> BaseFunctionSetType;
+  static const bool needs_grid_view = true;
 
 private:
   friend class PdelabWrapper<GridViewImp, polynomialOrder, RangeFieldImp, rangeDim, rangeDimCols>;

dune/gdt/space/interface.hh

@@ -48,6 +48,8 @@ public:
   typedef Stuff::GridboundaryInterface<IntersectionType> BoundaryInfoType;
   typedef Dune::Stuff::LA::SparsityPatternDefault PatternType;
 
+  static const bool needs_grid_view = Traits::needs_grid_view;
+
 public:
   /**
    * \defgroup interface ´´These methods have to be implemented!''