Easy way to listen context dispatch

```as3
override public function listEventInterests():Array
{
  return [FileEvent.DOWNLOADING, FileEvent.UPLOADING];
}

override public function handleEvent(event:Event):void
{
  switch(event.type)
  {
    case FileEvent.DOWNLOADING:
      // do something
      break;
    case FileEvent.UPLOADING:
      // do something
      break;
  }
}
```

Instead of
```as3
override public function initialize():void
{
  addContextListener(FileEvent.DOWNLOADING, _onFile_DownloadingHandler);
  addContextListener(FileEvent.UPLOADING, _onFile_UploadingHandler);
  // a lots of addContextListener 
}
```

Same as `PureMVC` event instead notification.
It's just idea without unit testing.
What do you think?