Give PHUITwoColumnView an addPropertySection method

Summary: Simplifies building pages a little more, adds a helper method to just add a property section to the main column automatically above other content.

Test Plan: Review Ponder, Herald, Passphrase, Countdown.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D15377