- removed Prometheus metrics stuff
- removed .cdn-util (might get added back later???)
- renamed and added a lot of configuration variables
- added Elasticsearch metrics collection in metrics/
- changed structure of metrics to include more data
    - GeoIP country
    - response status code
    - object type accessed
    - wildcard-stripped hostname (like before)
- metrics are collected as records per-request rather than a counter
  per-domain

- Add /.cdn-util endpoint (protected by key)
- Add Prometheus metrics (disabled by default) under /.cdn-util
- Replace configuration loader with Viper, config files are now
  supported
- Rename some config flags + environment variables