Commits
Only significant changes are in :::makeSensitivityImage(Lattice<T>, ImageInterface<Float>) signature.
The new code now uses LatticeIterator to (1) average all poln planes per freq. channel of the weight image and write it back to only the first poln plane per freq. channel of the weight image, and (2) copy the first poln. plane per freq. channel from the weight image to all poln planes per freq. channel of the sensitivity image. This should fix the problem of (a) I-PB and V-PB showing jump due to squint, and (b) PB in a freq. cube scales with frequency. (cherry picked from commit 039447bcf8c2d6dc6f465c270227bf49031be326)