Add basic BABE consensus type (#2165)

* Add basic BABE consensus type

* Update core/consensus/babe/slots/Cargo.toml

Co-Authored-By: DemiMarie-parity <48690212+DemiMarie-parity@users.noreply.github.com>

* Fix parameterization and run `rustfmt`

* Respond to review comments

* Update various Cargo.lock files

* Revert "Update various Cargo.lock files"

This reverts commit af53d7624752a744320e9cbb25749fdd8e6f46d2.

* `BabeSealSignature` → `BabeSeal`

* Move slot code to its own crate

This was highly non-trivial, due to cyclic dependencies.

* Remove redundancy between AuRa and BABE

Some of the code duplication was removed using a macro.

* Fix build error

* Avoid non-`#[doc(hidden)]` re-exports

Also, bump some library versions in `Cargo.toml`.

* Remove dead code in AuRa

* Remove impl_slot macro

It was more trouble than it was worth.

Also, delete useless dependencies on Serde.

* AuRa and BABE need different DB keys

* Bring back `aura::Network`, but deprecate it.

* Improve docs and add `slot_duration` inherent method

* Add docs to `substrate_consensus_aura::SlotDuration`

* Add missing documentation and #![forbid(missing_docs, unsafe_code)]

* Add a #![forbid(missing_docs)]

* Remove dependency of `test-runtime` on `slots`

* Update core/consensus/babe/src/lib.rs

Co-Authored-By: DemiMarie-parity <48690212+DemiMarie-parity@users.noreply.github.com>

* Remove wrongly added file

* Fix copyright notice

Co-Authored-By: DemiMarie-parity <48690212+DemiMarie-parity@users.noreply.github.com>

* Bump `impl_version` and `spec_version`

* Fix deprecation version; remove spurious carets

* Update Cargo.lock

* Update dependencies

substrate/core/consensus/babe/primitives/src/lib.rs

@@ -0,0 +1,76 @@
+// Copyright 2019 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Primitives for BABE.
+#![forbid(warnings, unsafe_code, missing_docs)]
+#![cfg_attr(not(feature = "std"), no_std)]
+
+use runtime_primitives::ConsensusEngineId;
+use substrate_client::decl_runtime_apis;
+
+use parity_codec::{Encode, Decode};
+
+/// The `ConsensusEngineId` of BABE.
+pub const BABE_ENGINE_ID: ConsensusEngineId = [b'b', b'a', b'b', b'e'];
+
+/// Configuration data used by the BABE consensus engine.
+#[derive(Copy, Clone, Hash, PartialEq, Eq, Debug, Encode, Decode)]
+pub struct BabeConfiguration {
+	slot_duration: u64,
+	expected_block_time: u64,
+}
+
+impl BabeConfiguration {
+	/// Return the expected block time in milliseconds for BABE.  Currently,
+	/// only the value provided by this type at genesis will be used.
+	///
+	/// Dynamic expected block time may be supported in the future.
+	pub fn expected_block_time(&self) -> u64 {
+		self.expected_block_time
+	}
+
+	/// Return the slot duration in milliseconds for BABE.  Currently, only
+	/// the value provided by this type at genesis will be used.
+	///
+	/// Dynamic slot duration may be supported in the future.
+	pub fn slot_duration(&self) -> u64 {
+		self.slot_duration
+	}
+}
+
+#[cfg(feature = "std")]
+impl slots::SlotData for BabeConfiguration {
+	/// Return the slot duration in milliseconds for BABE.  Currently, only
+	/// the value provided by this type at genesis will be used.
+	///
+	/// Dynamic slot duration may be supported in the future.
+	fn slot_duration(&self) -> u64 {
+		self.slot_duration
+	}
+
+	const SLOT_KEY: &'static [u8] = b"babe_bootstrap_data";
+}
+
+decl_runtime_apis! {
+	/// API necessary for block authorship with BABE.
+	pub trait BabeApi {
+		/// Return the configuration for BABE.  Currently,
+		/// only the value provided by this type at genesis will be used.
+		///
+		/// Dynamic configuration may be supported in the future.
+		fn startup_data() -> BabeConfiguration;
+	}
+}