eucalyptus.3-wb-1.9.0

Added

• Allow serving static files via a CDN
• Add django-redis-sentinel-redux to allow the use of Redis Sentinel for
  Django cache

Changed

• Collect static files in the edxapp image so it can run without mounting a
  volume for its static files in Kubernetes
• Configure most Django cache backends to Redis

Removed

• Remove now useless Memcached settings