Add a QQuickWidget - QQuickView comparison example

Besides serving as a side-by-side test tool for QQuickView and
QQuickWidget (including multisampling), it also demonstrates some
useful practices for rendering 3D content via QQuickFramebufferObject.

Done-with: Paul Olav Tvete <paul.tvete@digia.com>
Change-Id: Ie73e998ee91e32ef1535dd6f0f65c8a69addcc5e
Reviewed-by: Paul Olav Tvete <paul.tvete@digia.com>