Properly create Elasticsearch index

Summary:
When the index does not exist and auto_create_index isn't
enabled, running ./bin/index results in a failure. That's
T5990

Instead create an index properly. This also allows us to do
nice things like do a proper mapping and analysis like for
substring matching like outlined by @fabe in T6552.

Test Plan:
Deleted and created index multiple times to verify
proper index creation and usage.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, manybubbles, chasemp, fabe, epriestley

Differential Revision: https://secure.phabricator.com/D10955