R1:5df5f3390962

Add a task count to workboards

Summary: See Q335. This might need some tweaking, but the JS works now so we can move/style the node now.

Test Plan:
{F1169168}

- Also dragged stuff around, saw counts update properly.

Reviewers: chad

Reviewed By: chad

Differential Revision: https://secure.phabricator.com/D15462