add coefficient type to DefaultProblemTraits

src/amdis/ProblemStatTraits.hpp

@@ -57,10 +57,11 @@ namespace AMDiS
   } // end namespace Impl
 
   /// An Exemplar for ProblemStatTraits
-  template <class GlobalBasisType>
+  template <class GlobalBasisType, class T = double>
   struct DefaultProblemTraits
   {
     using GlobalBasis = GlobalBasisType;
+    using CoefficientType = T;
   };