Unable to pass more than one key=value argument to user creation

I was trying to create a new user from paster, passing all the user information on the command line, but:

```
% paster --plugin=ckan user --config=$VIRTUAL_ENV/etc/ckan/production.ini add admin apikey=my-admin-api-key password=admin email=admin@example.com
You must provide no more than 4 arguments
>>> exited 2
```

Apparently, user creation only works when passing **exactly** one extra argument: ``email`` (which is required). The password will be then asked with prompt, etc.

I had a look at the code, and this is due to ``max_args = 4`` being (incorrectly) set on the ``UserCmd``  command (incorrrectly as it is supposed to accept a variable number of arguments).