Add lower level for boot-strapping to RungeKuttaExteriorRV - Add a lower level to RungeKuttaExteriorRV for which bootstrapping starts, e.g start bootstrapping from time level 3 using a 3rd order BDF - Clean up ResidualViscosity

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