Show file cacheability in Files application

Summary: Ref T5685. We've added a new `canCDN` flag to control whether or not files can be cached and delivered over a CDN. Show this flag in the UI.

Test Plan: Viewed several files, saw correct/expected UI values.

Reviewers: btrahan, 20after4

Reviewed By: 20after4

Subscribers: epriestley

Maniphest Tasks: T5685

Differential Revision: https://secure.phabricator.com/D10213