Remove crons

[lahdekorpi]

System wide crontab (in /etc/crontab) should be cleared.

Also, I don't think there is any need for any scheduled tasks in this kind of system, so removing the "anacron" and "cron" packages wouldn't be a bad idea.

[ypcs]

Currently package ninja has dependency for cron. However, for Ninja to function, it doesn't really need cron. And yes, it's true, usually system uptime is something between 3-6 hours, so we won't need anacron/cron.

Create new metapackage which Provides: cron? Compile Ninja without this requirement? Other?