R1:e40bcc8d2bae

update documentation for storage changes w/ .php files

Summary: no schema changes allowed in the .php files

Test Plan: viewed doc -- looked good.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2059

Differential Revision: https://secure.phabricator.com/D3966