Add ability to archive a Dashboard

Summary: Let's people archive unused Dashboards (if they have permission).

Test Plan: Archive and Unarchive a dashboard, view history, view search, build new filters.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T6443

Differential Revision: https://secure.phabricator.com/D13683