feat #  prototype for section refresh animation

implementation of the section refresh animation
This condition should be moved to `insertHTML`. What has to be done in case an animation is already in progress is exactly the same as what has to be done when there is no animation. So the condition in `insertHTML` can become:

```js
if (this._cfg && this._cfg.animation && options && !options.skipAnimation && !this._animating) {
   // ...
} else {
   // replaceHTML may change domElt (especially on IE)
   domElt = aria.utils.Dom.replaceHTML(domElt, this.html);
   this.setDom(domElt);
}
```