Maximized window, and integration possibilities for the C++ compositor

 * possibility to maximize a card window, and to go back using gesturearea
 * better code organization so  that using an external window should be possible

Signed-off-by: Christophe Chapuis <chris.chapuis@gmail.com>
QML: use default webOS-Ports background image

Signed-off-by: Christophe Chapuis <chris.chapuis@gmail.com>