add a workaround to support x/y attributes for [draw image]

This should fix issue #452 (closed).

We add an additional above the normal one for the [draw image] parent and then just translate by x/y to simulate x/y on all the children. This is kind of weird because no other scalar drawing command acts this way. But there shouldn't be any side-effects with the current design since this DOM state gets destroyed when the scalar's container is removed.