Create initial qldarch entailment as copy of rdfs_lite.pl
Fix error in entailment/rdfs_lite.pl

select ?s ?c where { ?s rdfs:subClassOf ?o . } would return an
instantiation error in entailment/rdfs_lite.pl. This is thrown
because rdf_reachable(S, rdfs:subClassOf, O). is only valid where
one of S and O are bound.

Add atom() check to existing clause, and added new rdf/3 clause to
correctly handle the case where both are variable.
Merge branch 'rdfs_lite-fix' into qldarch
Using remote's rdfs_lite.pl
Fix basic entailment tests to reflect new reconcilations