Remove timestamp from config dump
    
    This makes it hard to programatically access the dump.
    
    The timestamp was included originally to make sure that restarting a
    compose in debug mode will preserve all configs. However we don't really
    support that usecase anyway.
    
    JIRA: COMPOSE-3063
    Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>