-Added configuration warning system for nodes

-Added a new "add" and "instance" buttons for scene tree
-Added a vformat() function to ease translation work

scene/2d/path_2d.h

@@ -109,6 +109,8 @@ public:
 	void set_cubic_interpolation(bool p_enable);
 	bool get_cubic_interpolation() const;
 
+	String get_configuration_warning() const;
+
 	PathFollow2D();
 };