[TIMOB-19642] Enable access to ListItem child views

For an example, see this Q&A issue: http://developer.appcelerator.com/question/159217/is-it-possible-to-animate-a-view-inside-a-listitem I also tried using the postlayout event on a ListItem child view to grab the event source to then animate it. No success. Thus the feature request would be to provide an event that signals when the view is "live" (i.e. something like postlayout), so we can then do something with it. Additionally, it may be useful to get a "view recycled" event when the ListView code recycles the cells - so for example we can stop animating. To highlight this issue: for example, it's impossible to use the images property on an ImageView in a ListItem, since we can't call the ImageView.animate() method.