ENH: Update level tracing effect on mouse wheel event
Created by: vovythevov
This allows the level tracing effect to be updated when the user scrolls through the slices.
On the implementation: Note that the method processViewNodeEvents is used instead of adding the events with the MouseMoveEvent as the MouseMoveEvent eats the event (abortEvent == True) which prevent the slice from scrolling. If the MouseWheelForwardEvent and MouseWheelBackwardEvent are given their own case (without abortEvent == True) weird interaction happen as the effect preview is seemingly called before the slice has scrolled to the new offset.