References in Attribute filtering

[Rod Widdowson]

Did we come to the conclusion that we should not support
"PolicyRequirementRuleReference", "AttributeRuleReference",
"PermitValueRuleReference" and "DenyValueRuleReference"?

I'd like to remove all the vestigial parsing support we put in and tie this
off with a failure.  As a reminder - this could never have worked in V2
because of schema issues and has never been documented.

Rod