KBestExtractor: get correct NT strings for parser output
KBestExtractor: get correct NT strings for parser output

The NTs used for the second-pass parse won't be in the Vocabulary, so
we need to calculate the appropriate string ourselves.

lukeorland/joshua,lukeorland/joshua,gwenniger/joshua,lukeorland/joshua,lukeorland/joshua,gwenniger/joshua,gwenniger/joshua,kpu/joshua,kpu/joshua,thammegowda/incubator-joshua,kpu/joshua,thammegowda/incubator-joshua,fhieber/incubator-joshua,thammegowda/incubator-joshua,thammegowda/incubator-joshua,lukeorland/joshua,fhieber/incubator-joshua,thammegowda/incubator-joshua,thammegowda/incubator-joshua,gwenniger/joshua,fhieber/incubator-joshua,thammegowda/incubator-joshua,thammegowda/incubator-joshua,fhieber/incubator-joshua,kpu/joshua,kpu/joshua,fhieber/incubator-joshua,thammegowda/incubator-joshua,lukeorland/joshua,fhieber/incubator-joshua,lukeorland/joshua,fhieber/incubator-joshua,fhieber/incubator-joshua,lukeorland/joshua,thammegowda/incubator-joshua,fhieber/incubator-joshua,lukeorland/joshua,gwenniger/joshua,kpu/joshua,gwenniger/joshua