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.

% Plots all the eigen values for a sparse matrix.
function plotEig(A)
    e = eig(full(A));
    e = sort(e);
    plot(e,'.')
end