use Window QML Type as root item instead of Rectangle.
use QQmlApplicationEngine to simplify the startup code to load the main qml file
some cleanups
fixed maximize(fullscreen toggle) of the main window
added another UI version for the example viewer
created a model for the examples instead of define it in each qml ui.
c++ified the generation of the Fxaa fragment shader code (no need for explicit new/delete ;))