R1:7dd19ba93fb6

Convert AphrontFormLayoutView to safe HTML

Summary: Searched for `AphrontFormLayoutView` and then `appendChild()`.

Test Plan: /V1

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2432

Differential Revision: https://secure.phabricator.com/D4856