Security Policy Changes

[Mike McGrath]

I've added some patches (mostly more better English :) to the security
policy.

I've also added an "Administrative Exceptions" section to deal with the
following valid use-cases:

 - Password sharing (like that of the mailman admin password)
 - Role accounts (for Ian and our wiki bot account)
 - Policy for other non-user passwords (like those of our webapps
   contacting the database)

Please comment on clarity and logic:

http://infrastructure.fedoraproject.org/csi/security-policy/en-US/html-single/#EndUser-Standard-Admin-Exceptions

	-Mike