Validator/authority contract (#3937)

* dir

* simple validator list

* stub validator contract

* make the engine hold Weak<Client> instead of IoChannel

* validator set factory

* register weak client with ValidatorContract

* check chain security

* add address array to generator

* register provider contract

* update validator set on notify

* add validator contract spec

* simple list test

* split update and contract test

* contract change

* use client in tendermint

* fix deadlock

* step duration in params

* adapt tendermint tests

* add storage fields to test spec

* constructor spec

* execute under wrong address

* create under correct address

* revert

* validator contract constructor

* move genesis block lookup

* add removal ability to contract

* validator contract adding validators

* fix basic authority

* validator changing test

* more docs

* update sync tests

* remove env_logger

* another env_logger

* cameltoe

* hold EngineClient instead of Client

* add a comment about lock scope

json/src/spec/validator_set.rs

@@ -0,0 +1,47 @@
+// Copyright 2015, 2016 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity 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.
+
+// Parity 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 Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Validator set deserialization.
+
+use hash::Address;
+
+/// Different ways of specifying validators.
+#[derive(Debug, PartialEq, Deserialize)]
+pub enum ValidatorSet {
+	/// A simple list of authorities.
+	#[serde(rename="list")]
+	List(Vec<Address>),
+	/// Address of a contract that indicates the list of authorities.
+	#[serde(rename="contract")]
+	Contract(Address),
+}
+
+#[cfg(test)]
+mod tests {
+	use serde_json;
+	use spec::validator_set::ValidatorSet;
+
+	#[test]
+	fn validator_set_deserialization() {
+		let s = r#"[{
+			"list" : ["0xc6d9d2cd449a754c494264e1809c50e34d64562b"]
+		}, {
+			"contract" : "0xc6d9d2cd449a754c494264e1809c50e34d64562b"
+		}]"#;
+
+		let _deserialized: Vec<ValidatorSet> = serde_json::from_str(s).unwrap();
+	}
+}