Initial fork versioning (#934)

* Merge #913

* Correct release tests

* Completed release test corrections

* Initial work on upgrading discovery

* Updates discovery to latest version

* Update ENR initialisation logic

* Remove debug statements

* Shifts timing units to slots

* Initial work

* Add initial fork versioning and EnrForkId

* Correct linking for EnrForkId

beacon_node/fork/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "fork"
+version = "0.2.0"
+authors = ["Age Manning <Age@AgeManning.com>"]
+edition = "2018"
+
+[dependencies]
+types = { path =  "../../eth2/types" }