[security-services] Attribute syntax/scoping

I promised to follow-up Phill HB's latest suggestions regarding
attribute value syntax, with respect to Shibboleth's requirements. After
further discussion and thinking about the problem, I believe the best
idea is to keep the scope issue out for the time being.

As long as SAML continues to support the original value syntax using the
<any> schema element, we can embed any necessary syntax in the XML. Any
advantage gained from explicitly calling out the scope in the schema
would be minimal unless others see the benefit in it, and it may be best
to consider it later in light of other work in this area, perhaps in
XACML.

So we have no issue at this time, as long as the proposal on the table
doesn't eliminate the <any> formulation, regardless of what else gets
added (or not).

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  Scott Cantor               So long, and thanks for all the fish.
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