Allow users to "Edit a Copy" when trying to edit a panel they don't own
Summary:
Fixes T5167. When clicking "Edit" on a dashboard panel you don't own, the UI now allows you to make a copy instead.
As a bonus, fixes T5259.
Test Plan: See screenshots.
Reviewers: chad
Reviewed By: chad
Subscribers: epriestley
Differential Revision: https://secure.phabricator.com/D9505