Add block rewards to more Engines (#4055)

* add block rewards

* imports

json/src/spec/authority_round.rs

@@ -30,6 +30,9 @@ pub struct AuthorityRoundParams {
 	pub step_duration: Uint,
 	/// Valid authorities
 	pub authorities: Vec<Address>,
+	/// Block reward.
+	#[serde(rename="blockReward")]
+	pub block_reward: Option<Uint>,
 	/// Starting step. Determined automatically if not specified.
 	/// To be used for testing only.
 	#[serde(rename="startStep")]
@@ -49,12 +52,13 @@ mod tests {
 	use spec::authority_round::AuthorityRound;
 
 	#[test]
-	fn basic_authority_deserialization() {
+	fn authority_round_deserialization() {
 		let s = r#"{
 			"params": {
 				"gasLimitBoundDivisor": "0x0400",
 				"stepDuration": "0x02",
 				"authorities" : ["0xc6d9d2cd449a754c494264e1809c50e34d64562b"],
+				"blockReward": "0x50",
 				"startStep" : 24
 			}
 		}"#;