ArgsInterpreter: Usage message for single-command mode

[rolandweber]

The usage message for the single-command mode is poorly constructed. There's no place to describe the behavior or the single command before the arguments are listed.

Example output from a Follow-the-Board client:

Command-line arguments:
<host> <port> [<arg> [...]]

where:
<host> - hostname or IP address to connect to
<port> - port number to connect to

Arguments:
[<interval>]
  follow the board, with polling interval in seconds

The Arguments: line is provided by the base class. Maybe just remove that, so the command handler can provide a description as suitable?

[rolandweber]

Simply removing the Arguments: line won't do. Further up, the [<arg> [...]]is also provided by the base class. After the Arguments: line follows a more detailed description of what these arguments are.

Maybe allow the single command to supply a replacement for [<arg> [...]]?