R1:b987b4dd64f5

Rudamentary PHUILeftRightView

Summary: First pass at providing a skeleton framework for laying out basic items in a left/right view. Will likely add some mobile-responsive options.

Test Plan: UIExamples

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D18200