Create residual viscosity package +rv and generalize the ResidualViscosity class - Generalize residual viscosity, by passing user-defined flux and calculating the time derivative outside of the update. - Create separate RungekuttaRV specifically using interior RV updates - Separate the artifical dissipation operator from the scheme AdvectionRV1D so that the same scheme can be reused for creating the diff op used by the ResidualViscosity class

% Creates a matrix of size n,m with the values of val on the diagonals diag.
%   A = stripeMatrix(val,diags,n,m)
function A = stripeMatrix(val,diags,n,m)
    default_arg('m',n);

    D = ones(n,1)*val;
    A = spdiags(D,diags,n,m);
end