Rearchitecture of the window manager and the card view

 * WindowManager component is now almost empty
 * CardView component manages all the card-related actions
 * Simplification of the window wrapper, which only manages the state and focus of the window
 * No more reparenting of the wrapped window when maximizing of fullscreen:
    the delegate component now expands nicely to fit the wanted place
 * The delegate now handles the look of the window wrapping
 * Focus management, along with current window information, is more easily reached
 * Dashboard windows have not been fully integrated; needs more design work
 * Test objects have been updated

Note: this has only been tested on QML desktop. A fix commit will follow after on-device testing.

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