Add general Runge-Kutta class - Add a general Runge-Kutta class which time integrates the solution based on coefficients obtained from a Butcher tableau - Add butcher tableau which returns coefficents for the specified Runge-Kutta method - Remove RungKutta4proper, since obsolete

% Discretises a shape such that points on the curves are no further than h appart.
function p = shape_discretise(s,h)
    p = [];
    for i = 1:length(s)
        [~,pt] = parametrization.curve_discretise(s{i},h);
        p = [p, pt];
    end
end