Spoilers: support for previews and nested spoilers

- found a much better solution to bind the events which is right when the
  spoiler element is created (no need for livequery)
- replaces all occurences of .bind() with .on() (which is the preferred way
  as of jQuery 1.7)
- adds support for spoilers in comment previews, but needed a few workarounds
  to accomplish this:
  - the PreviewLoaded js event is fired before the preview is loaded into the
    dom, so I added a 150ms delay to the FindAndReplace() call which should be
    enough for every browser to load the DOM
  - the AfterCommentPreviewFormat event lacks the ['Object']->Body EventArgument
    I created it in the hook so the RenderSpoilers() function doesn't need  to be
    changed
- tested in Firefox, IE and Chrome