Homestyx hydra

R1:64234535e3c9

Remove FIELD_KEYWORDS, index project slugs as body content

Summary:
D17384 added a "keywords" field but only partially implemented it.

- Remove this field.
- Index project slugs as part of the document body instead.

Test Plan:
- Ran `bin/search index PHID-PROJ-... --force`.
- Found project by searching for a unique slug.

Reviewers: chad, 20after4

Reviewed By: chad

Differential Revision: https://secure.phabricator.com/D17596
Repository: R1 hydra
Commit Date: Apr 2 2017