Improve elasticsearch

Summary: I thought that this will be fun but the elasticsearch API is horrible and the documentation is poor.

Test Plan:
Search for:

• string
• author
• author, owner
• string, author
• open
• string, open, author
• string, exclude
• several authors, several owners
• nothing
• probably all other combinations

Normally, such an exhaustive test plan wouldn't be required but each combination requires a completely different query.

Reviewers: epriestley, jungejason

Reviewed By: epriestley

CC: aran, Koolvin, btrahan

Differential Revision: https://secure.phabricator.com/D2298