Cosmetic improvements to help

[tlberglund]

The help text takes up a bit too much vertical space. The below might be an improvement. Also, responding to --help on the command line would be a nice tweak.

Usage: confluent <command> [<subcommand>] [<parameters>]

These are the available commands:

    list        List available services.
    start       Start all services or a specific service along with its dependencies
    stop        Stop all services or a specific service along with the services depending on it.
    status      Get the status of all services or the status of a specific service along with its dependencies.
    current     Get the path of the data and logs of the services managed by the current confluent run.
    destroy     Delete the data and logs of the current confluent run.
    log         Read or tail the log of a service.
    top         Track resource usage of a service.
    load        Load a connector.
    unload      Unload a connector.
    config      Configure a connector.

'confluent help' lists available commands. See 'confluent help <command>' to read about a
specific command.```