R1:72d12be8500c

Update Legalpad with modern UI

Summary: Updates Legalpad Manage/Edit with new UI layouts.

Test Plan: Wrote a new document with and without a preamble, edit document, sign document

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D15576