Add ability to create elastic search JSON

Summary:
 - Use harvests2json and a compressed mws index, one can generate
 annotated JSON documents which can be used in elasticsearch.
 - closes #28

Test Plan:
./bin/mws-index -I ./data/zbl/ -o Index/
./bin/harvests2json -I Index/ -H ./data/zbl

Reviewers: cprodescu

Reviewed By: cprodescu

Differential Revision: http://phab.code4fun.de/D68
Fix memory leak in LevFormulaDb.
Save compressed index directly to disk.

Summary:
 - The previous implementation required the compressed index
 to be built in memory
 - closes #27
 - closes #30

Test Plan:
bin/mws-index -I data/zbl -o data/compressed
bin/mwsd-load -I data/compressed &
scripts/send-qvar-query.sh 9090 0 0

Reviewers: radu.hambasan, m.iancu

Reviewed By: m.iancu

Differential Revision: http://phab.code4fun.de/D67