Role: ansible-role-postgresql-backup

[joshmoore]

See:

• ome-dundeeomero backup script Fix: can't use sudo from /etc/cron #279
• https://github.com/openmicroscopy/ansible-role-mysql-backup/blob/master/templates/etc-crond-mysql-backup.j2

The production server playbooks currently have logic for creating a backup cronjob. This is a prime candidate for refactoring into a role. (Also a good entry task for anyone wanting to learn ansible)