Relying party parsing. Metadata providers

[Rod Widdowson]

> >- I am getting increasingly unhappy at adding referenced to OpenSAML and
> >idp-saml-impl to the idp-profile-spring package.  

I should add that Ian has just reminded me of a further discomfort - the
precise package included by idp-profile-spring is opensaml-saml-impl.  So
this is doubly wrong.  There is an explicit derogation that idp-*-spring
modules may depend on idp-*-impl modules, but it feels slightly icky to
depend on an opensaml-*-impl module.

> I would think it's most sensible to have a SAML module for parsing the
> metadata configuratiom, if that really breaks any links from idp-profile-*
> to any SAML classes.

I'll look as see whether the RelyingParty and ProfileConfiguration need
idp-saml-impl, and if not I'll suggest growing an idp-saml-spring class.  Of
course that then asks the question of whether other SAML specific
configuration should go there (such as the encoders, the NameID attribute
resolvers and so on).  

Rod