[security-services] Core-21

Attached are the core-21 draft and the two schemas.

Phill kindly let me "own" core-21 after he put in the agreed-to technical 
changes, and I did a bunch of editorial things to it.  You'll find that the 
overall "look" (and, somewhat, the organization) of the core draft has 
changed to match the other specs more closely.  My goal was to stick to 
changes that were technically neutral (for example, there is still a notion 
of single/multiple assertions); if you find any instances where I 
accidentally changed a meaning, let me know.

I will separately be making a bunch of substantive comments/questions, 
hopefully before tomorrow's meeting so that we can discuss and decide on 
some of them.  I believe I'll have time to do a core-22 before I go on 
vacation December 13-18 if such is required, and Phill will return from his 
IETF meeting after next week, so that will be the handoff point.

	Eve