Add support for artificial viscosity to the 1d burgers scheme. - Add support for artificial viscosity by parametrizing the discretization operator and boundary closure on the viscosity. - Add a time stepper which evaluates and updates the residual viscosity of the solution.

% Plot a shape using n points. Returns cell array of plot handles.
%   hs = plot_shape(s,n)
function hs = plot_shape(s,n)
    default_arg('n',100);

    hs = {};
    hold on
    for i = 1:length(s)
        hs{end+1} = grid.plot_curve(s{i},n);
    end
    hold off
end