[security-services] Here is a draft of the SAML Concepts section

I realized once I started writing that this is the kind of conceptual text 
that people could have fist fights over... :-)  I'm hoping that my warning 
that it's merely "informational" will allow us to get to something that's 
usable in core-24.  That said, I would really appreciate it if people could 
glance at it and tell me/Phill if it's in the right direction.  If it's not 
close to okay, it's probably better to leave a hole in Section 1.3 than to 
try to come up with something else.

Please note: The bibliographic citations in here are fake because I wrote 
this standalone.  Phill, if you use this, please be sure to replace all the 
bold [foo] items with real cross-references.

Oh, one other note: The graphic uses color because I repurposed the one 
from my presentation.  If color is no good in printed versions, I can 
remove it.

	Eve