Dedupe DIRECTORY w/ Directory tab in directory header

Summary: the tab is a bit silly right next to DIRECTORY

Test Plan:
viewed phabricator with an admin account

• looks good on load
• clicked Categories and Items; looked good

viewed phabricator with a non-admin account

• looks good on load
• nothing else to click in the header

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, epriestley

Differential Revision: 1131