Draft implementation of RungeKutta with exterior RV updates - Draft class RungeKuttaExteriorRV which updates the residual using a BDF approximation of the derivtive outside of the RK stages. - Draft class for BDF derivative

% Converts a gridfunction to a plot matrix
% Takes a grid function and and a structured grid.
function F = funcToPlotMatrix(g, gf)
    F = reshapeToPlotMatrix(gf, g.size());
end