SCUBA2: display only as many decimal places as needed

The default display format for values is 5 decimal places, which is
overkill for plots with values plotted every 50 arcsec or so. Instead
set the format WCS attribute to pick the most suitable number of
decimal places (%g) which leads to cleaner-looking displays.
sun264: expand FCF calculation description with actual parameters used

List the actual parameters used in the calls to beamfit and autophotom
so that others may attempt to reproduce the pipeline results by hand.