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

function y = rickerWavelet(x, x0, A)
    y = (1-2*pi^2*A^2*(x-x0).^2).*exp(-pi^2*A^2*(x-x0).^2);
end