Add default up direction

docs/api/core/Object3D.html

@@ -66,7 +66,7 @@
 
 		<h3>[property:Vector3 up]</h3>
 		<div>
-		Up direction.
+		Up direction. Default is THREE.Vector3( 0, 1, 0 ).
 		</div>
 
 		<h3>[property:Matrix4 matrix]</h3>