Add a zooming behavior for ClientCanvas

[DavidRoehl]

Could you add a zooming behavior to Client Canvas just like the
onLabel( label ).useZoom() or is there a way on Canvas with the same effect?

Right now we have the Problem that our Images are too big, so we have to resize them manually(same size than canvas) to get them into the canvas area. But with resizing them the quality of the Images is getting really bad and they look distortet.