Add RK6 with residual viscosity update and reduce computational effort of spatial scheme - Add RK6 with residual updates - Change the D2 operator for upwind schemes to one less computationally expensive.

function saveFigurePosition()
    defaultPosition = get(0,'defaultfigureposition');
    f = gcf;
    defaultPosition(3:4) = f.Position(3:4);
    set(0,'defaultfigureposition',defaultPosition);
end