Outdated warning for clamav is only shown with warning level in monitor when the daily.cfd update failed as well.

Catch situation where no basic awstats configuration can be found
and create a warning message.

add database-size monitoring. the results stored in the database may be used to add the db-size to the web-quota, too.

- Added dkim installation to installer.
- Added backup filesize in backup cronjob.

- Implemented: FS#3110 - Turn monitoring module into cron jobs