Use ManifestStaticFilesStorage for Cache Busting

[wesleyboar]

Is your feature request related to a problem? Please describe.

• CMS can serve stale content to users when we update our styles.
• Running collectstatic can do no-op instead of overwriting files.
  — @jarosenb

Describe the solution you'd like
Set ManifestStaticFilesStorage as the backend, so our static files will have hashed filenames.

Describe alternatives you've considered
?

Additional context

• Django docs ManifestStaticFilesStorage
• Use ManifestStaticFilesStorage for cache busting #648
  • simple status of #648
  • detailed status of #648

[wesleyboar]

Documented so I can close #648 (which was forever open as reminder).