refactor lua usertypes

src/logic/scripting/lua/lua_commons.hpp

@@ -48,4 +48,9 @@ namespace lua {
 
     void log_error(const std::string& text);
 
+    class Userdata {
+    public:
+        virtual ~Userdata() {};
+        virtual const std::string& getTypeName() const = 0;
+    };
 }