[interfaces.grid-function] add ctor and fix doc

dune/xt/functions/interfaces/grid-function.hh

@@ -65,7 +65,7 @@ class ProductGridFunction;
  *
  *        We follow one strong assumption in dune-xt-functions: after being localized to an element, a local function
  *        (or a set of local functions) has to provide the order which is required to integrate it _exactly_ on this
- *        element, and it _should_ thus coincide with polynomial of respective on an element. While there exists
+ *        element, and it _should_ thus coincide with a polynomial of respective order on an element. While there exists
  *        non-polynomial data functions, we only have quadratures of finite order and no way to detect
  *        discontinuities of functions (thus the order of the local polynomial approximation must be provided). This
  *        encourages the user to really think about the data functions when implementing/using them, but avoids
@@ -98,6 +98,11 @@ public:
   using DifferenceType = Functions::DifferenceGridFunction<ThisType, ThisType>;
   using SumType = Functions::SumGridFunction<ThisType, ThisType>;
 
+  GridFunctionInterface(const Common::ParameterType& param_type = {})
+    : Common::ParametricInterface(param_type)
+  {
+  }
+
   virtual ~GridFunctionInterface() = default;
 
   static std::string static_id()