Grafana integration (#3913)

* Very WIP

* record_metrics macro works

* Integrate into service

* Licenses and documentation

* Remove unused Debugs, make respond function clearer

* Conform to line widths, fix service test

* Switch to storing the timestamps as millis instead

* Update core/grafana-data-source/src/lib.rs

Co-Authored-By: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Transform timestamps to i64 in serialization

* Fix license date

* Binary sort to find selection range for metrics

* Obey maxDataPoints

* Run a cleaning future

* Newlines at EOF

* Update core/service/Cargo.toml

Co-Authored-By: Pierre Krieger <pierre.krieger1708@gmail.com>

* Update core/grafana-data-source/src/lib.rs

Co-Authored-By: Pierre Krieger <pierre.krieger1708@gmail.com>

* Fix indentation

* Improve select_points

* Made test more accurate

* Inprogress

* Use the same futures version as hyper for now

* Error handling

* Remove dependence on hyper's tokio feature

* Added target_os flag

* Update Cargo.toml

Co-Authored-By: Pierre Krieger <pierre.krieger1708@gmail.com>

* Simplify example

* Remove compat wildcard

* Updated lock file

* Fix indentation 😉

substrate/client/grafana-data-source/Cargo.toml

@@ -0,0 +1,24 @@
+[package]
+description = "Grafana data source server"
+name = "grafana-data-source"
+version = "2.0.0"
+license = "GPL-3.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+edition = "2018"
+
+[dependencies]
+hyper = { version = "0.13.0-alpha.4", default-features = false, features = ["unstable-stream"] }
+tokio-io = "0.2.0-alpha.6"
+tokio-executor = "0.2.0-alpha.6"
+futures-util = { version = "0.3.1", default-features = false, features = ["io"] }
+futures-util-alpha = { package = "futures-util-preview", default-features = false, version = "0.3.0-alpha.19" }
+serde_json = "1"
+serde = { version = "1", features = ["derive"] }
+chrono = { version = "0.4", features = ["serde"] }
+lazy_static = "1.4"
+parking_lot = "0.9"
+futures-timer = "2.0"
+derive_more = "0.15"
+
+[target.'cfg(not(target_os = "unknown"))'.dependencies]
+async-std = { version = "1.0.1", features = ["unstable"] }