Use Window as top-level qml element.

Fixes the problem with background not beeing redrawn when resizing.

Had to use QQmlApplicationEngine instead of QQuickView. The docs says that
Window instantiates a QQuickWindow. I interpret the docs for QQuickView as "a
container for drawables". Can it be that Window is differs from the other qml
components?
Imitate Google+ colors for the searchbar.