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

% Sorts x with respect to the function d
% d is a function that accepts an element of x and returns a scalar.
function y = sortd(d,x)
    v = [];
    for i = 1:length(x)
        v(i) = d(x(i));
    end

    [~,I] = sort(v);
    y = x(I);
end