In Curve: Added numerical FD differentiation if derivative is not supplied. Added arc length computation based on the derivative. Added arc length parameterization (but this function is very slow.). In +util: Added fzero_vec.m and integral_vec.m, which call fzero and integral but take vector arguments.

function place_label(pt,str,horzAl,vertAl)
    default_arg('horzAl','center');
    default_arg('vertAl', 'middle');

    x = pt(1);
    y = pt(2);
    h = text(x,y,str);
    h.HorizontalAlignment = horzAl;
    h.VerticalAlignment = vertAl;
end