Add a 'title' sort option to Maniphest

Summary:
Allow sorting tasks by title in addition to priority, updated,
created.

Test Plan:
Load Maniphest, click between order buttons, note that tasks
are being ordered correctly, as if by magic.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T1592

Differential Revision: https://secure.phabricator.com/D3137