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.

% runs f for each value in v and plots the result.
function plotfv(f,v,opt)

    if ~exist('opt')
        opt = '';
    end

    for i = 1:length(v)
        y(i) = f(v(i));
    end
    plot(v,y,opt)
end