Migrate Project workboard to modular transactions
Summary: This was interesting, because there were a mix of callsites using transactions and others that just set the property on the `Project` object. I made everything consistent in using transactions to change this property. I also found an implementation of `getTitle()` that I don't think is ever being invoked since `shouldHide()` is returning `true`, but I migrated it anyway.
Test Plan: Unit tests pass + enabling/disabling workboards (and importing).
Reviewers: #blessed_reviewers, epriestley
Reviewed By: #blessed_reviewers, epriestley
Subscribers: epriestley
Differential Revision: https://secure.phabricator.com/D18004