Convert database to UTF-8

Summary: This is the script used for conversion: P319

Test Plan:
Update diff with UTF-8 characters in description.
sql/upgrade_schema.php
Verify data in DB and that it looks good on web.

Reviewers: epriestley, nh

Reviewed By: epriestley

CC: aran, epriestley

Maniphest Tasks: T327

Differential Revision: https://secure.phabricator.com/D1830