Allow searching Dashboards by Editable

Summary: Ref T10390. I find myself wanting to find dashboards I can edit, even if I am not the author. I think this is useful for larger installs with multiple admins. Also make disabled Dashboards more grey in UI results.

Test Plan: Log in a test user, create a dashboard with I cannot edit. Log into my account, search for editable dashboards and only see mine. Set dashboard to all users, search under test account and see editable dashboards.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T10390

Differential Revision: https://secure.phabricator.com/D17524