Automatic observer for autocompleter prototype (in collections)

Hi.
I wrote a patch for automatic observing of *autocompleters* if they are generated from prototypes of collections. Because it is a little bit annoying if you always have to write extra code for such cases.

`jQuery.on()` is used to observe autocompleters which are generated dynamically from prototypes. Performance impacts should be very low (see http://www.brentsowers.com/2012/03/jquery-on-performance.html).

There's only one problem: This patch will generate javascript code for every prototype fields (not only for autocompleters). But I do not know how to achieve that :-( maybe someone has a better idea.