Add some test coverage for board moves

Summary: Ref T10010. This isn't totally comprehensive, and a lot of behaviors aren't testable (e.g., all the Javascript stuff) but at least covers the basic create/move/reorder operations.

Test Plan: arc unit

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10010

Differential Revision: https://secure.phabricator.com/D15178