changelogs: Implement custom compose sorting
    
    Productmd will not work if there are composes with different name. We
    however know that all of them have an identical short, so can make a few
    assumptions. The ordering that would be used (if not for the name
    difference) is version, then compose date, type and finally respin.
    
    JIRA: COMPOSE-1950
    Change-Id: Ife4e54453b7fe3b42ff5e4e957b063ab9098cf84
    Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>