Punish offline validators, aura-style (#1216)

* make offline-reporting infrastructure more generic

* add a listener-trait for watching when the timestamp has been set

* prevent inclusion of empty offline reports

* add test for exclusion

* generate aura-offline reports

* ability to slash many times for being offline "multiple" times

* Logic for punishing validators for missing aura steps

* stub tests

* pave way for verification of timestamp vs slot

* alter aura import queue to wait for timestamp

* check timestamp matches seal

* do inherent check properly

* service compiles

* all tests compile

* test srml-aura logic

* aura tests pass

* everything builds

* some more final tweaks to block authorship for aura

* switch to manual delays before step

* restore substrate-consensus-aura to always std and address grumbles

* update some state roots in executor tests

* node-executor tests pass

* get most tests passing

* address grumbles

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

@@ -0,0 +1,50 @@
+// Copyright 2017-2018 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 Aura.
+
+#![cfg_attr(not(feature = "std"), no_std)]
+
+extern crate parity_codec as codec;
+extern crate substrate_client as client;
+extern crate substrate_primitives as primitives;
+extern crate srml_support as runtime_support;
+extern crate sr_io as runtime_io;
+extern crate sr_primitives as runtime_primitives;
+
+/// The ApiIds for Aura authorship API.
+pub mod id {
+	use client::runtime_api::ApiId;
+
+	/// ApiId for the AuraApi trait.
+	pub const AURA_API: ApiId = *b"aura_api";
+}
+
+/// Runtime-APIs
+pub mod api {
+	use client::decl_runtime_apis;
+	decl_runtime_apis! {
+		/// API necessary for block authorship with aura.
+		pub trait AuraApi {
+			/// Return the slot duration in seconds for Aura.
+			/// 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() -> u64;
+		}
+	}
+}