heterodyne: Inquire all the subscans in an observation.

It previously could flag a receptor as bad if just one of the subscans
of an observation was entirely bad for that receptor.  It now flips
the loops to process all the files for each receptor, concatenate the
spectra for the receptor before obtaining statistics.
heterodyne: Introduce a means to prevent creation of moments maps.
general: It's a general routine now so remove UKIRT-specific limitation comment.
general: Move one-off operations outside the file loop.
general: Add primitive to enable provenance recording.

This addition is mainly for UKIRT reductions at CADC.
imaging: Enable provenance recording.
ifu: Enable provenance recording.
ifu: Add some comments.

It's still missing a prologue...
spectroscopy: Enable provenance recording.
heterodyne: Commit the working version from January.
JSA: Obtain the JSA_TILES header from the chosen object.
JSA: Add a note saying how the primitive decides the naming mode.

The mode being whether it's JSA tiling or not.

Also update copyright date and authors.
heterodyne: Add missing NDFCOPY to enable the integration to work.

This fixes a bug which sometimes prevented masking of astronomical
emission, which in turn caused otherwise flat spectra to be rejected
as non-linear.  See Scicom Ticket 383 for `before' and `after' images.
heterodyne: Remove residual debugging line.