Adding liszt:reset event to reset chosen without rebuild

I had the need to reset the state of chosen but not rebuild the entire list of items. This need came up when a user needed to reset the form, and the chosen list present in the form had quite a few items. So it was not ideal to incur the expensive time rebuilding the list again.

I noticed you had a reset method exposed on the object but no observer to invoke it. So I merely added an observer to be able to do so

$('form_field").trigger('liszt:reset');
or
Event.fire($("form_field"), "liszt:reset");

Let me know if this makes sense.
Thanks.