Add tasks to install script/tarsnap configuration file and a cronjob to run
the backup job
Number of hourly/daily/weekly/monthly backups kept can be configure from the
tarsnap.sh script

Thanks to this script, we don't use all the backups which save space on
tarsnap server and thus reduce the price to pay

Sovereign does not currently use jabber/xmpp or insecure smtp.

That way the default values will not be applied by mistake. The user
needs to uncomment the lines from `vars/users.yml` and set them.

Also renamed openvpn variables.

Refs #39

Refs #39

(such as root's cron errors)

Fix CAcert usage in postfix and dovecot

Fix Postfix configuration file to link to correct SSL certificate locations

Removed your hardcoded server IP

The old action would generate a crontab job for `* 3 * * *`, which means every minute at 3am, so 60 times per day.

Thanks @pjan