Aurorae goes QML

What's working:
* background for active and inactive decorations inclusive transitions
* all buttons get loaded
* transition between button states
* all borders, paddings etc is working
* mouse interaction with buttons and title area

What's not yet working:
* special maximize mode
* mouse wheel on title area
* window tabs
* changing themes
* crash resistence (currently a not compiling QML file crashes KWin badly)
* window/blur mask (tricky - we need the alpha mask of the background SVG)

What's going to be dropped:
* special opaque mode
* decoration position at left/right/bottom instead of top
Why? Because nobody uses these features