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

% 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