AttributeResolver and Resolver API

[Cantor, Scott]

Revisiting this for a sec, I was expecting to find that it was equally
tortured to make the lookup interface for RelyingPartyConfig a Resolver
subtype because it would need access to an entire ProfileContext tree.

What I forgot was that the base Resolver API is actually fully generic to
the type of criteria you give it. The case of CriteriaSet used in most of
our existing examples is just arbitrary.

The current "resolver" for RelyingParty config actually takes a
ProfileRequestContext as the second parameter.

So I suspect it might not be too tortured to do something similar with the
AttributeResolver, but only if it made additional sense, which I'm not
sure it does. In particular the Resolver API really just has the resolve()
and resolveSingle() methods, while I'm guessing the AttributeResolver is
defined to populate a subcontext to return the attributes. So I'm still
not sure it makes any sense. Just wanted to note it.

-- Scott