add field for tie_breaker_id to elasticsearch and use that for search_after

see #44 (closed)

plan of action:

1. add new field tie_breaker_id to elasticsearch mapping
2. update elasticsearch dev with mapping
3. update elasticsearch test with mapping
4. update elasticsearch prod with mapping
5. let esutils take care of copying id to new field
6. run a script to copy existing id's to new field on dev
7. run a script to copy existing id's to new field on test
8. run a script to copy existing id's to new field on prod
9. use new field for search_after in tgsearch