2D Animation Improvements

-=-=-=-=-=-=-=-=-=--=-=-=

-Ability to set 2D nodes as bones
-Abity to set 2D nodes as IK chains
-2D IK Solver
-Improvements in the UI for adding keyframes (separate loc,rot,scale buttons)

scene/scene_string_names.h

@@ -128,6 +128,7 @@ public:
 	StringName offset;
 	StringName unit_offset;
 	StringName rotation_mode;
+	StringName rotate;
 	StringName v_offset;
 	StringName h_offset;