Added MANIFEST for slackware64-14.1
Added SLACKWARE variable
Added check_manifest function to check MANIFEST's integrity
Remove unnecessary user accounts after checking from MANIFEST, that they
are not being used

Got the motivation to add this, after I noticed Monkeysphere creates
/var/lib/monkeysphere/authorized_keys/operator, as the user operator has
"/root" as home dir (if root has authorized_keys):

ms: ----- user: operator -----
ms: checking for authorized_user_ids...
ms: empty or absent authorized_user_ids file.
ms: checking for raw authorized_keys...
ms: checking path permission '/root/.ssh/authorized_keys'...
ms: checking '/root/.ssh/authorized_keys'
ms: checking '/root/.ssh'
ms: checking '/root'
ms: stopping at operator's home directory '/root'
ms: adding raw authorized_keys...
ms: moving new file to /var/lib/monkeysphere/authorized_keys/operator...
Merge branch 'manifest'