Auth: log module name with IRMA log entries

[reinkrul]

Suggested change in irmago: privacybydesign/irmago#232

[woutslakhorst]

But if we configure our logger to do JSON, then this logger will still do text?

[reinkrul]

But if we configure our logger to do JSON, then this logger will still do text?

No it will output as JSON: the JSONFormatter is set on the StandardLogger before the auth module is initialized, and this code copies the StandardLogger and wraps the Formatter (text or JSON) with a decorator that adds a field. The wrapped formatter will simply be the JSON formatter.