support running a sequence of Maven builds in dependency order
    
    The new "koji chainmaven" command allows Maven builds to be run in depdencency order,
    without needing to wait for repo regens.  A config file specifies the parameters and
    dependencies for each build in the sequence.  Each build is launched as soon as all
    dependent builds are complete, and is able to reference the output of all of its
    dependencies.  If the build source URL and parameters match the latest build of the
    same package in the destination tag, the build will not be re-run.