use different special query for rdf:ID

returning triples with URI rdf:ID URI instead of SUBJECT rdf:type
rdf:Resource. This turns some case handling wrt rdf:ID unnecessary, but
the code should still work.
outcomment unnecessary code
extend test case for rdf:ID
delete deprecated method
extended rdf:ID test by normal P2GAM test
Merge pull request #68 from janpolowinski/34-generalize-rdf-ID-usage

34 generalize rdf id usage