Fixed name handling in OpenIdOAuthProvider

When retrieving attributes from an OpenID 2.0 source, names were not
being handled well. This change ensures that fullName explicitly uses
the first of "http://schema.openid.net/namePerson",
WellKnownAttributes.Name.FullName, or WellKnownAttributes.Name.Alias to
return a value. Where none of these are present but
WellKnownAttributes.Name.First and/or WellKnownAttributes.Name.Last are
provided, these will be concatenated to infer a fullName.