Add Dashboards as a default pinned application

Summary: Ref T10390. Dashboard usability is high enough that I think we should pin it by default for users to create custom home pages.

Test Plan: Review order of applications in sandbox.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T10390

Differential Revision: https://secure.phabricator.com/D17527