Add support for artificial viscosity - Add option to use upwind operators for discretizing the scheme - Add option to use dissipation operators constructed from undivided differences when discretizing with narrow stencil operators

function e = errorSbp(discr, v1, v2)
    % If v1 and v2 are more complex types, something like grid functions... Then we may use .getVectorFrom here!
    H = discr.H;
    err = v2 - v1;
    e = sqrt(err'*H*err);
end