Merge branch 'issue/bugfixes' into 'develop'

Issue/bugfixes

See merge request spraetor/dune-amdis!10

src/amdis/Initfile.hpp

@@ -29,7 +29,7 @@ namespace AMDiS
         return pt().get<T>(key);
       }
       catch (...) {
-        return Dune::Std::nullopt;
+        return {};
       }
     }
 

src/amdis/utility/Traversal.hpp

@@ -4,6 +4,8 @@
 #include <dune/typetree/treepath.hh>
 #include <dune/typetree/visitor.hh>
 
+#include <amdis/common/Loops.hpp>
+
 namespace AMDiS
 {
   // forward declaration of main engine struct