Global events are firing on add/remove links pre-/post-execution

Hey,
merge this if you think someone has a use besides me. This was a big help to me, because I was able to daisy chain events triggered after the fields were added. Like hiding elements and so on. I think it is useful when the code is purely event driven. I placed the events into global scope (though, with a very unique name, to avoid clashes), since you haven't established a namespace yet. :) If you are planning on one, then don't merge, since that'll break compatibility.

Usage:
$(document).bind( [EVENT],function(){} ) where EVENT is:
nested_forms:fields_adding -> fires before new fields are added
nested_forms:fields_added -> fires after new fields are added
nested_forms:fields_removing -> fires before fields are removed
nested_forms:fields_removed -> fires after fields are removed