Introduced tabs and added the C++ boilerplate launcher.

Change-Id: Ibb49a182e3928aba5dced097d5307eb7d1f4b42d
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@digia.com>

Use system palette colors.  SimpleLauncherDelegate has its own "button"
rather than using the shared one, which really wasn't suitable for any other
purpose.  So now example apps can use Button, and ToolButton isn't necessary.

Change-Id: I632397f36b96a26c32a86301ddacb85d5c3221f0
Reviewed-by: Jens Bache-Wiig <jens.bache-wiig@digia.com>

This will obsolete the QFileDialogItem in desktop components and be
available to all QtQuick applications.  The QML FileDialog type is
dynamically defined in the plugin by detecting which implementation
will work on the current platform.

Change-Id: I073c7a84bff6c02cf592dc46822a5a4b9c9bcaea
Reviewed-by: Jens Bache-Wiig <jens.bache-wiig@digia.com>