R1:41875ce7b487

Collapse Dashboards to single column when durable present and narrow

Summary: Currently we punch down Dashboard columns on smaller displays. This adds another set of rules for if durable-column is present.

Test Plan: Test breakpoints at 1300 and 1000 pixel wide.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T7531

Differential Revision: https://secure.phabricator.com/D12056