Improve name handling from OpenID 2.0 sources

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.