New security policy additions

[Mike McGrath]

I've added a few things to the security policy.  Of particular interest
is:

http://infrastructure.fedoraproject.org/csi/security-policy/en-US/html-single/#HostGeneralSecurity-Security-Category

and

http://infrastructure.fedoraproject.org/csi/security-policy/en-US/html-single/#HostGeneralSecurity-System-Identification

As far as security categories go, I'm still working on what that should
mean for us.  But for now go ahead and read over the various categories
(there's only 3) and think about what hosts you'd put where and why.  We
can suss some of that out over the freeze and what it will mean.

	-Mike