[publican-list] --lang vs --langs

[Joshua Wulf]

>> What about a warning message, something like ``A single language
>> expected, using --lang instead''?
>>      
> I think the generic "that parameter can't be used with this action" is
> pretty clear. Again, to harp on, if you say --langs is a valid
> parameter, then you have to support people supplying a list of
> languages. Generating an error for a valid parameter that has a valid
> format is a bug.
>
>    
Can we make it prompt for the parameter if it is not supplied? That way 
I don't have to think about lang or langs, I just type the thing in when 
it asks for it.

Publican create would also be great with a wizard-like interface.