Comment #9 on issue 888 by tu...(a)tudorgirba.com: MondrianViewBuilder should
support a better zOrder
http://code.google.com/p/moose-technology/issues/detail?id=888
Indeed, all elements should be rendered independently of their nesting
level :).
That is why it is important to have the zIndex in the element, and ideally,
we should also store the order by level in the ZOrdering.