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.

% Run matlabs checkcode on all files in current folder including subfolders
function checkAllCode(d)
    default_arg('d','')
    files = findMfiles(d);
    checkcode(files)
end