Semantic parser improvements

[jayantk]

Adding several features to the semantic parser:

1. handling unknown words
2. reading in a separate table of known entity names (and using these in the parser)
3. new bidirectional LSTM seq2seq model w/ attention for scoring logical forms

These features improve accuracy on geoquery to ~78%, from ~35% before.

[OyvindTafjord]

Very cool, that's a decent improvement! :) Some things for future consideration:

• If we have frequent changes to jklol.jar, maybe we should keep that out of the repo and just update it locally
• Maybe use some sort of logging mechanism rather than explicit printlns in the code