Feed groups support

   The main focus of this release is the introduction of feed groups.

   It is now possible to declare one or more groups in the configuration file
   to list shared feed properties.  Individual feeds can inherit these
   properties of one or more feed groups, reducing redundancy in configurations.
   The configuration remains backwards compatible.

   See crossbow.conf(5) for specific details.

Minor changes

   The release includes a few minor fixes and improvements, mostly related
   to the configuration file parsing and to the build system.