CD-1 issue #28: PolicySet in RBAC profile

The issue number refers to the XLS-sheet found in this email:
http://lists.oasis-open.org/archives/xacml/200909/msg00013.html

The commenter thinks that the RBAC profile is unclear about whether a 
PolicySet is allowed in a Permission PolicySet.

I agree and I think we should change the text so it is clear that it is 
allowed.

Best regards,
Erik