Migrate to New Keyserver API

We have a new, more powerful, key server API in a feature branch of the keyserver repo. To migrate, I would suggest to:

• Deploy the new Keyserver to dev.key.metager.de
• Implement the new API in MetaGer and point at dev.key.metager.de endpoint
• Deploy the new Keyserver to key.metager.de
• Switch the endpoints for production and metager3 back to key.metager.de and dev.key.metager.de respectively