Add CloudFlare as a storage backend for quay.io

CloudFlare is a popular CDN with a unique offering in that it does not charge for the bandwidth for outgoing bytes but charges based on how much data you store on the CDN. This is very interesting for quay.io where cost for CloudFront has been a huge pain.

Develop a CloudFlare storage provider for quay/quay.io which can act as another CDN provider to quay.io