This is a straightforward operation that will copy the cubic spline or
polynomial coefficients from each IF from memory to the relevant
calibration section (-29 or -31, see Table 2) of the
hpb file (provided it was initialized at hpb creation). One can
override this default by forcing it to use a given sideband or
polarisation (or average of sidebands or polarisations) to calibrate
both polars/sidebands.
