Basic sync of family trees to elasticsearch

persons collection is synced to elasticsearch
- only persons considered as deceased are synced (according to existing is_living_person logic)
- person id in is stored in "PID" attribute in elasticsearch (because "id" has special meaning in ES)
added documentation in README regarding handling of databases and (ES) indexing
api v1/search endpoint supports persons
- for general search over all collections, add &with_persons=1 to get persons as well
- (to allow deployment without breaking the frontend)
- if you specify &collection=persons - it will return only persons (no need for with_persons)
- currently it only searches the person's name
ensure_required_metadata script should be used to sync the persons from mongo to elasticsearch
- changed --add-to-es parameter to --add
- added --legacy parameter which loads from legacy collections (should not be used on production)
- added --limit parameter which allows to load just a portion of data for testing
elasticsearch: added index of type keyword for the main doc id field
quicker tests by reusing the elasticsearch db (where possible)

Beit-Hatfutsot / dbs-back