Use BABE instead of AuRa in node (#3171)

* babe: add babe module trait

* babe: track current slot and epoch start slot

* babe: implement ShouldEndSession based on epochs

* babe: rename weight type to avoid ambiguities

* babe: expose epoch start slot in Epoch digest

* babe: use epoch start for validating epoch transitions

* babe: make the epoch duration a parameter type

* babe: remove unused fields from config

* node: update runtime to use babe instead of aura

* node: use babe instead of aura

* core: generate sr25519 keys from seed and add to keystore

* core: remove AuthorityKeyring

* node: remove unused primitive types related to babe crypto

* uniform babe primitives crate import name

* wrap long lines

* babe: fix find_epoch_digest

* fork-tree: fix find_node_where

* node: set babe epoch duration to "10 minutes"

* babe: cleanup import key cache if authorities don't change

* node: make integration test compile (but fail)

* node: bump spec_version

* node: fix import

* babe: don't use constants in storage fields array sizes

* babe: account for first epoch slot way in the past

* babe: signal next epoch change (not current)

* babe: calculate next epoch randomness with next epoch index

* babe: track next epoch in node

* babe: cache current epoch and authorities separately

* babe: generate valid babe vrf proofs in integration test

* babe: cleanup claim_slot

* babe: perform threshold calculation according to spec

* babe: compute relative weight in threshold

* babe: more precise threshold calculation

* babe: use floats for threshold exponent calculation

* babe: update constant c

substrate/Cargo.lock

@@ -2274,8 +2274,8 @@ dependencies = [
  "substrate-basic-authorship 2.0.0",
  "substrate-cli 2.0.0",
  "substrate-client 2.0.0",
- "substrate-consensus-aura 2.0.0",
- "substrate-consensus-aura-primitives 2.0.0",
+ "substrate-consensus-babe 2.0.0",
+ "substrate-consensus-babe-primitives 2.0.0",
  "substrate-consensus-common 2.0.0",
  "substrate-finality-grandpa 2.0.0",
  "substrate-finality-grandpa-primitives 2.0.0",
@@ -2360,8 +2360,8 @@ dependencies = [
  "sr-primitives 2.0.0",
  "sr-std 2.0.0",
  "sr-version 2.0.0",
- "srml-aura 2.0.0",
  "srml-authorship 0.1.0",
+ "srml-babe 2.0.0",
  "srml-balances 2.0.0",
  "srml-collective 2.0.0",
  "srml-contracts 2.0.0",
@@ -2380,7 +2380,7 @@ dependencies = [
  "srml-timestamp 2.0.0",
  "srml-treasury 2.0.0",
  "substrate-client 2.0.0",
- "substrate-consensus-aura-primitives 2.0.0",
+ "substrate-consensus-babe-primitives 2.0.0",
  "substrate-keyring 2.0.0",
  "substrate-offchain-primitives 2.0.0",
  "substrate-primitives 2.0.0",
@@ -2460,6 +2460,15 @@ dependencies = [
  "version_check 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "num-bigint"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "num-integer 0.1.41 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-traits 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "num-integer"
 version = "0.1.41"
@@ -2469,6 +2478,17 @@ dependencies = [
  "num-traits 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "num-rational"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "autocfg 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-bigint 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-integer 0.1.41 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-traits 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "num-traits"
 version = "0.2.8"
@@ -4335,6 +4355,9 @@ dependencies = [
  "futures-preview 0.3.0-alpha.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "merlin 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-bigint 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-rational 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-traits 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "parity-codec 4.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -6153,7 +6176,9 @@ dependencies = [
 "checksum nodrop 0.1.13 (registry+https://github.com/rust-lang/crates.io-index)" = "2f9667ddcc6cc8a43afc9b7917599d7216aa09c463919ea32c59ed6cac8bc945"
 "checksum nohash-hasher 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "0d138afcce92d219ccb6eb53d9b1e8a96ac0d633cfd3c53cd9856d96d1741bb8"
 "checksum nom 4.2.3 (registry+https://github.com/rust-lang/crates.io-index)" = "2ad2a91a8e869eeb30b9cb3119ae87773a8f4ae617f41b1eb9c154b2905f7bd6"
+"checksum num-bigint 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "57450397855d951f1a41305e54851b1a7b8f5d2e349543a02a2effe25459f718"
 "checksum num-integer 0.1.41 (registry+https://github.com/rust-lang/crates.io-index)" = "b85e541ef8255f6cf42bbfe4ef361305c6c135d10919ecc26126c4e5ae94bc09"
+"checksum num-rational 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "f2885278d5fe2adc2f75ced642d52d879bffaceb5a2e0b1d4309ffdfb239b454"
 "checksum num-traits 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)" = "6ba9a427cfca2be13aa6f6403b0b7e7368fe982bfa16fccc450ce74c46cd9b32"
 "checksum num_cpus 1.10.1 (registry+https://github.com/rust-lang/crates.io-index)" = "bcef43580c035376c0705c42792c294b66974abbfd2789b511784023f71f3273"
 "checksum numtoa 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b8f8bdf33df195859076e54ab11ee78a1b208382d3a26ec40d142ffc1ecc49ef"