undo using unordered map for primitive storage

src/hyteg/primitivestorage/PrimitiveStorage.hpp

@@ -111,7 +111,7 @@ class PrimitiveStorage : private walberla::NonCopyable
 {
  public:
    template < typename P >
-   using GenericPrimitiveMap = std::unordered_map< PrimitiveID::IDType, std::shared_ptr< P > >;
+   using GenericPrimitiveMap = std::map< PrimitiveID::IDType, std::shared_ptr< P > >;
    typedef GenericPrimitiveMap< Primitive > PrimitiveMap;
    typedef GenericPrimitiveMap< Vertex >    VertexMap;
    typedef GenericPrimitiveMap< Edge >      EdgeMap;