ArMem: Use DictDataNavigator instead of general DataNavigator in EntityInstance and related types

• EntityInstance
• EntityUpdate

This opportunity can also be used to check/fix the RemoteGuiAronDataVisitor:

        template <class Navigator>
        void addValueLabel(Navigator& n, const std::string& typeName)
        {
            # groups.empty() should not occur
            if (not groups.empty())
            {
                groups.top().addChild(Label(this->makeValueLabelText(n, typeName)));
            }
        }