weak initial attempt at API doc
Allow build-astrometry-index and solve-field to read xylists from an extension other than 1 -- first by trying to add -e args to uniformize.py, removelines.py, etc, but then by writing a temp file containing just the extension of interest.
Change augment-xylist.h 'outfn' member to 'axyfn'; add --temp-axy option to solve-field
solve-field: add --axy output filename option