Remove comments; amend rotation interval

The comments in this file are already well documented; they serve little purpose
in-line in the file, and add extra overhead if the commands are ever changed.

The rotation interval has been changed to weekly; we keep a year's worth (52
weeks) of logs before logrotate rotates them. This was done for security
purposes.
Add AppArmor profile for clamd

In a similar vein to [this Puppet pull
request](https://github.gds/gds/puppet/pull/557), this commit:

- adds AppArmor
- allows read access with /srv/backup-data
Remove AppArmor

AppArmor profiles were a bit of a red-herring, it seems. This commit removes
them.
Amend clamscan program

`clamscan` and `clamdscan` have subtle differences, it seems. The former is
meant to be run as one-off and in cron jobs; the latter is daemonized. The
former also processes the virus definitions each time it runs; the latter does
not.

`clamdscan` doesn't support the --exclude switch, whereas `clamscan` does. To
that end, the command has been changed to support `clamscan`, thereby allowing
us to exclude `lost+found` as we do not particularly care about data stored
within that folder.