Make image of calibrator field

It would be useful to have an image produced of the flux calibrator field at the end of LINC calibrator pipeline (preferably at 6" or 20").

This would enable one to check the flux scaling (i.e. by comparing images with other surveys, otherwise we're relatively blindly assessing the calibration outputs). Other stretch benefits include multi-frequency imaging to build more refined models with better in-band spectra (i.e. with WSClean -fit-spectral-pol), and assessing more advanced calibration methods (e.g. bandpass self-calibration, as has been suggested to improved instrumental calibration for MeerKAT).

Having the calibrated measurement sets being saved to disk would also be a good starting point to allow users to make images of the calibrator field in post-processing.