R1:f7c381358656

Add Label MenuItem

Summary: Ref T12174, lets you set labels as well for dividing content.

Test Plan: Add a label, review on homepage.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T12174

Differential Revision: https://secure.phabricator.com/D17278