Updating UserGuide with Kerberos v5 authentication

Updating UserGuide with Kerberos v5 authentication

This patchset contains updates to the OpenAFS UserGuide that
explains how to authentication OpenAFS using kinit/aklog
and uses language describing Kerberos outside the context
of the kaserver.  References to applications such as telnet
have been replaced with more modern equivalents such as ssh.

Change-Id: Ifae779b04a26beb9be9cf58b450958acdc477c06
Reviewed-on: http://gerrit.openafs.org/1521
Tested-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>