Make PHUITwoColumnView a little more printable

Summary: Hide navbar, and make curtain behave like on a phone, when printing.

Test Plan: {F5197340}

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D18583