Send appropriate requests to the server when dragging cards on project boards

Summary: Ref T1344. Makes requests to the server, which are received and ignored. Performs appropriate locking/unlocking/enabling/disabling on the client.

Test Plan: Dragged stuff around, saw it enable/disable/send correctly.

Reviewers: chad, btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T1344

Differential Revision: https://secure.phabricator.com/D7943