R1:df2c015e7cff

Make Dashboard tab panels editable by humans

Summary: Fixes T5335. This is not pretty, but should reasonably let normal humans create tab panels.

Test Plan: See screenshot.

Reviewers: chad

Reviewed By: chad

Subscribers: epriestley

Maniphest Tasks: T5335

Differential Revision: https://secure.phabricator.com/D9600