Publish event.state.changed.min message
    
    Some clients load incoming UMB messages into an environment variable.
    Since environment variables have a system dependent size restriction,
    the existing event.state.changed message can easily exceed it.
    
    This change makes Freshmaker publish an **additional** message that is
    much smaller. It does so by omitting the list of builds associated with
    the event. Instead, it provides a summary of total builds count as well
    as builds count for each state. Clients loading received messages in
    environment variables should use the new message.
    
    Although the new message provides sufficient details for clients to find
    out the list of builds, some clients already exist that rely on this
    information to be in the message directly. For this reason, both
    messages are now sent.
    
    Signed-off-by: Luiz Carvalho <lucarval@redhat.com>