fix Button touch event wihin an invible parent; and really support Enabl...

...ed/Disabled state

case1: Button touch event still be triggerable when its parent (or parent of parent ..) is invisible.

case2: Widget has enabled property, but there is no edit item for it on UIEditor, and Widget use it to judge draw or not. I guess it might be misuse. because, once change a widget's enabled to false, it will disappear on the screen. so what's the different between these two properties 'enabled' and 'visible'?

and, Button support to set disabled image on UIEditor, but unable to show it base on the property 'enabled' on the screen.