distribute calib object uniformly over the FoV in netflow

As we discussed back in April/May, we would like to distribute the standard fibers and sky fibers uniformly in the FoV.  I vaguely remember that netflow did not have that capability, but it would be trivial to implement it (correct me if I am wrong). He-san recently pointed out that I did not file a ticket for that. So, here it is.