[xacml] 16f change requests

Schema v16f updates:

Ann:

Change Request:

  Add an identifier for an Action Attribute that 
means that the
  Action to be performed is contained in or implied by 
the name
  of the Resource.

Change Request:

  In context-16f.xsd, the AttributeValue element 
does not have a
  DataType xml attribute.  I request that this be 
added.

Simon:

16g: Issuer of Attribute is xs:string

16g: Action element reference in Target (was not a global element)

16g: PolicyIdReference 

16g: PolicySetIdReference

16g: DataType attribute for AttributeSelector

16g: Pass <SubjectAttributeDesignator> as an argument to 
<Apply>.

Simon