cli: mention --profile in --config help text
    
    It's easy for new users to confuse the "--config" and "--profile"
    settings.
    
    We want to guide users towards using non-default profile names (eg
    "stream" or "cbs", etc) where possible. If a user is pointing at a
    non-standard configuration file location, they should really use the
    --profile option also to keep their configuration sane.
    
    Update the --help text for the --config option to emphasize the
    --profile option.