Headword and JWI wordnet utils

Added Niranjan's headword extraction code, which also depends on wordnet and what use to be called WordNet-Demo, which is a simple wrapper over jwi wordnet library to do some synonym bits.

- HeadExtractor will do some magic to determine headwords from args (argumentHead()) and rels (relationHead())
- JwiTools uses WordNet to lookup synonyms and hypernyms.