JSA::Headers: extract prepare_header_updates

Extracted the logic for preparing the FITS header updates from
JSA::Headers::Starlink::update_fits_headers to make a new function
JSA::Headers::prepare_header_updates.  This new function simply
returns a collection of [header, value, comment] arrays.
JSA::Headers::FITS: add header update function

Created a new module "JSA::Headers::FITS" containing a function
which updates the headers of FITS files in the same way as is
done by the "JSA::Headers:Starlink::update_fits_headers" function.
Update MANIFEST
JSA::Files: add mode argument to can_send_to_cadc

can_send_to_cadc is called before the association type is updated
(e.g. from night to public).  This means that when it calls
_can_send_to_cadc_quick, it gives the wrong association type
for group products when not in obs or night modes.  It looks like
this can only be corrected by passing the mode to can_send_to_cadc
so that it can update the mode as read from the file when
necessary.
JSA::Files: do not check OBS_TYPE in public mode
JSA::Files: use given mode in can_send_to_cadc

Now use the specified mode instead of the file's association
type if that is "night" in order to take account of cases when
this function is run before the association type header has
been updated.
JSA::Files: allow conversion of extent-mask

This is now allowed as a public product.  The patterns for
co-added JSA tile files have been expanded to match [-a-z]+ in place
of just "healpix".

Note that - is included in this pattern match.  If this character
is problematic then we will need to rename these files.
JSA::Files: use 6-digit product counts for pub
JSA::Files: escape . in JSA tile DR file regexps
JSA::Files: add looks_like_fits_drfile function
JSA::Headers::FITS: export header update function
JSA::Convert: add support for FITS products
JSA::Files: add JSA catalog product names
JSA::Files: allow - in CADC file product names

This is to allow dpCapture to capture the new catalog products.