SCUBA2: write the pattern name for scan observations

The vast majority of SCUBA-2 data is taken in SCAN mode - therefore
the "mode" entry in the log file isn't particularly useful. Instead,
write out the name of the scan pattern - either daisy or
pong. Non-scan observations will still have the observation mode
written to the log file.
SCUBA2: store fit FWHM manually

The auto-store option only works if no other values have been stored
previously. Therefore fall back on the tried and tested way of doing
things by specifying the values to be stored at the time they need to
be stored.