[CALIBRATE\]APPLY AMPLI [Gain] [/FLAG [Threshold]]
Apply an Amplitude gain calibration result. In doing so, the weights
are never up-scaled, even when the Amplitude correction factor is small-
er than 1. They are down-scaled for visibilities with correction factor
larger than 1. The rationale behind this behaviour is to avoid giving
more weights to data which has been modified in a self-calibration
process.