Add a config and script for Rawhide done with DNF
    
    This is a temporary measure for testing. It will shadow real rawhide
    composes and redo them with depsolving based on DNF.
    
    The composes will land in /mnt/koji/compose/rawhide-dnf and there will
    be logs with information about changes in package set.
    
    Nothing will be sent to fedmsg, no mails will be sent.
    
    Only the package set is created, no extra images or even repos are
    created.
    
    Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>