Update Legalpad to use modular transactions

Summary: Update Legalpad for modular transactions

Test Plan:

• New Document (no sign)
• New Document (individual)
• New Document (corp)
• Require Signature - get prompted to sign before I can do anything.
• Edit Documents
• Sign Documents
• Comment on Documents

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D17826