Add prometheus metrics

[adria0]

Implements #11725

• New trait PrometheusMetrics implemented it in Client and EthSync
• Hyper server for serve metrics in parity/metrics.rs, metrics be accessed via http://...:3000/metrics, only for full client (not implemented for light client)
• Command line flags for metrics, disabled by default, port and interface can be configurated
• Docker-compose for starting the client with metrics in scripts/prometheus, contains grafana/prometheus visualization. Go to the folder and run docker-compose up.
• New snapshot creation status .restoration_status() , so renamed .status() to .creation_status().

[vorot93]

I think we should try hyper 0.13 with https://github.com/paritytech/parity-common/pull/403

[adria0]

I think we should try hyper 0.13 with paritytech/parity-common#403

@vorot93 Done. Please check https://github.com/openethereum/openethereum/tree/adria0/prometheus-tokio-compat