Puppet will now add a cron job and configure logrotate to backup
etherpad-lite's MySQL DB daily and keep a months worth of backups.
These are the defaults and are slightly configurable through the
etherpad_lite::backup class.
Also configure log rotation for etherpad-lite's error.log and
access.log.
Change-Id: I30e0a4c8ee852e6621ee74744968d85696658608
7b299b2af1