Added triggerEvent option without bubbling

Hello,
In my use case i found it handy to add a trigger(event) on hidden element value change.
That was causing bubbling and "too much recursion" errors, so I added  the triggerEvent option with 'change' as the default value. Also, I modified the script so the trigger(event) is able to work independently of the fieldset. You can listen the event with jQuery .live() and you can use custom events. It is also working with multiple birthdaypickers simultaneously. I have also added some functionality that prevents multiple hidden elements of the same region in cases of new dynamically added birthdaypickers.