Update Fund for EditEngine

Summary: Ref T12685, updates fund for edit engine.

Test Plan: Create a Fund, Edit a Fund, wipe out Merchants, check errors for name and missing merchants, back Fund.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T12685

Differential Revision: https://secure.phabricator.com/D17855