[TED] Core Horn Rules Edited for Slot/Constraint Removal and XML Derivation

In preparation of the 1st Core WD, I continued with edits re 4) of
http://lists.w3.org/Archives/Public/public-rif-wg/2007Jan/0111.html
by removing slots/constraints from the Core page on Horn Rules;
to support the XML derivation from a 'fully striped' abstract syntax,
I also inserted roles in the 'Forall' formula (*):
http://www.w3.org/2005/rules/wg/wiki/Core/Horn_Rules?action=diff&rev2=3&
rev1=2

-- Harold

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(*) Meanwhile, the two-level CORE hierarchy was copy-pasted into a 
    single-level Core hierarchy, so the new Core entry point now is
    http://www.w3.org/2005/rules/wg/wiki/Core (FrontPage is updated).