[Core] XML Schemas Added to RIF-Core

I have added initial XML schemas to RIF-Core:
http://www.w3.org/2005/rules/wiki/Core#Appendix:_XML_Schema_for_RIF-Core

The linked directory also contains some (counter)examples.

Official test cases can now be delineated for this second RIF dialect,
where several existing BLD test cases will already belong to Core:
http://www.w3.org/2005/rules/wiki/Category:Test_Case

Changhai, you can have a first look, consider how it specializes RIF-BLD
(which itself specializes RIF-FLD), and how to generalize it to RIF-PRD.

Chairs, please put a Core XSD review (15 mins?) on the 24 March agenda.

-- Harold