Add lower level for boot-strapping to RungeKuttaExteriorRV - Add a lower level to RungeKuttaExteriorRV for which bootstrapping starts, e.g start bootstrapping from time level 3 using a 3rd order BDF - Clean up ResidualViscosity

function print_issparse(A)
    warning('Deprecated! Use printExpr() instead!');
    b = issparse(A);
    if b
        s = 'true';
    else
        s = 'false';
    end
    fprintf('%8s is sparse: %s\n',inputname(1),s);
end