Improve QGraphicsView's mouse replay mechanism

QGraphicsView's mouse replay mechanism is based on reposting the QMouseEvent to the QGraphicsView. This doesn't make much sense; instead the replay should go straight from the view to the scene. The scene event should be replayed, not the view event.

The reason today's replay approach doesn't make sense, is that when users create a subclasss of QGraphicsView, and catch events, they tend to get many identical events when they transform or scrolll the view. Which doesn't make sense at all.