Summary: Depends on D20408. Ref T13272. The actual JS is still a little bit iffy, but this makes the server side "move" operation work correctly by updating it to use the same code as everything else.

Test Plan: Moved panels around on single-column and multi-column dashboards, saw them move to reasonable places and stay there when I reloaded the page.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13272

Differential Revision: https://secure.phabricator.com/D20409