Add nologin sketch Adds sketch to prevent non privledged users from logging into the system. Facilities for all users (/etc/nologin) and individual users (nologin shell) are provided as seperate entry points.

[nickanderson]

etc_nologin entry tested by me on master.stage successfully

[tzz]

Thanks!

[zzamboni]

Thanks. Other than the typo in sketch name indicated in my comments, this seems good.