Add 'verbosity' keyword argument to astrometry_net()
Update help text of the -v / --verbose option
Remove unused variable 'fd'
Add 'ra' keyword argument to astrometry_net()
Add 'dec' keyword argument to astrometry_net()
Add 'radius' keyword argument to astrometry_net()
Document 'ra', 'dec' and 'radius' in the docstring of astrometry_net()
Add optparse.OptionGroup 'coords_group'
Add --ra option
Add --dec option
Add --radius option
Update Bash completion support for the 'astrometry' command

This should have been done in commit 2215beb729865039ec16.
Force --ra and --dec to be used together or not at all
Force --radius to be a positive number
astrometry_net(): add options --ra, --dec, --radius and --verbosity

If the approximate coordinates of the image are known, the execution
of Astrometry.net can be substantially sped up by restricting the
search to those indexes within a certain number of degrees of the
(estimated) field center.

This merges branch 'astrometry-improvements'
Remove --update option
Accept multiple input FITS images, do astrometry on all of them
Add --suffix option
Use median of solved RAs and DECs to approximate field coordinates
Update help text of the 'coords_group' optparse.OptionGroup