Make sky, horizon, flakes and clouds optional, replace repeated strips of skyL/skyR with 2x2 transparent PNGs instead of larger images of variable dimensions, remove a number of empty unused images

#include <QtGui/QApplication>
#include "mainwindow.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}