SCUBA2: log.mapstats has columns for rms and nefd units.

log.mapstats files create by picard will correctly write the units
into the header of the table. However, if it is run on a second
file with different units it doesn't indicate the change in units.
This commit moves the RMS and NEFD units into columns in the table.
It also adds in a column for the RECIPE fitsheader.
SCUBA2: print filename in log.mapstats entries.

As new log.mapstats calls have their results concatenated into an
existing file, it can be easy to not notice if you've run it on the
wrong file. Adding in the filename to the results should help a little
for users who are running this manually with the PICARD recipe rather
than in the ORAC-DR reduction pipeline.