Adds ENR "eth2" field and Fork logic to networking (#953)

* 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

* Adds eth2 field to local ENR

* Initial work to eth2 field integration

* Integrate eth2 field into discovery

* temp commit

* Add a timer to adjust fork versions during a hard fork for the ENR

beacon_node/eth2-libp2p/Cargo.toml

@@ -8,7 +8,7 @@ edition = "2018"
 hex = "0.3"
 # rust-libp2p is presently being sourced from a Sigma Prime fork of the
 # `libp2p/rust-libp2p` repository.
-libp2p =  { git = "https://github.com/SigP/rust-libp2p", rev = "0cb9d504c7be6a7bcfc87feeafdb6847d8083fc6" }
+libp2p =  { git = "https://github.com/SigP/rust-libp2p", rev = "8c272a9a4d115d9a1d33791479527cdcba781829" }
 types = { path =  "../../eth2/types" }
 serde = "1.0.102"
 serde_derive = "1.0.102"
@@ -16,6 +16,7 @@ eth2_ssz = "0.1.2"
 eth2_ssz_derive = "0.1.0"
 slog = { version = "2.5.2", features = ["max_level_trace"] }
 version = { path = "../version" }
+# beacon_chain = { path = "../beacon_chain" }
 tokio = "0.1.22"
 futures = "0.1.29"
 error-chain = "0.12.1"