Project work boards - make editing tasks from workboards work

Summary: This wasn't working. Create a little JS handler and server-side support for returning the Task in the "project card" format.

Test Plan: Edited tasks from the board - they worked!

Reviewers: epriestley

Reviewed By: epriestley

CC: Korvin, epriestley, aran, chad

Differential Revision: https://secure.phabricator.com/D8392