R1:afc5333bb3aa

Convert AphrontFormView to safe HTML

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

Test Plan: /login/

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2432

Differential Revision: https://secure.phabricator.com/D4855