[Monocle] Added ILinkAnnotation.
[Monocle] No use in keeping annotations subclasses.
[Monocle] AnnRectGraphicsItem.
[Monocle] Invoke base mouse event handlers in annotations.
[Monocle] Added Link annotation.
[Monocle PDF] Pass Document to MakeAnnotation().
[Monocle PDF] Added LinkAnnotation.