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.

function A = kr(varargin)
    n = nargin;

    A = 1;

    for i = 1:n
        A = kron(A,varargin{i});
    end
end