R1:b9f394164f18

Add renderHTMLView

Summary:
- Implement AphrontView->renderHTMLView(), which works like AphrontView->renderSingleView() but always return PhutilSafeHTML.

Test Plan: Action list view no longer as broken.

Reviewers: vrana

Reviewed By: vrana

CC: aran

Differential Revision: https://secure.phabricator.com/D4642