Generalize the Consensus Infrastructure (#883)

* Split out Consensus
* Supply ImportQueue through network-service
  - simplify ImportQueue.import_blocks
  - remove Deadlock on import_block
  - Adding Verifier-Trait
  - Implement import_queue provisioning in service; allow cli to import
* Allow to actually customize import queue
* Consensus Gossip: Cache Message hash per Topic

substrate/core/service/src/chain_spec.rs

@@ -87,6 +87,7 @@ struct ChainSpecFile {
 	pub boot_nodes: Vec<String>,
 	pub telemetry_url: Option<String>,
 	pub protocol_id: Option<String>,
+	pub consensus_engine: Option<String>,
 }
 
 /// A configuration of a chain. Can be used to build a genesis block.
@@ -125,6 +126,10 @@ impl<G: RuntimeGenesis> ChainSpec<G> {
 		self.spec.protocol_id.as_ref().map(String::as_str)
 	}
 
+	pub fn consensus_engine(&self) -> Option<&str> {
+		self.spec.consensus_engine.as_ref().map(String::as_str)
+	}
+
 	/// Parse json content into a `ChainSpec`
 	pub fn from_embedded(json: &'static [u8]) -> Result<Self, String> {
 		let spec = json::from_slice(json).map_err(|e| format!("Error parsing spec file: {}", e))?;
@@ -152,6 +157,7 @@ impl<G: RuntimeGenesis> ChainSpec<G> {
 		boot_nodes: Vec<String>,
 		telemetry_url: Option<&str>,
 		protocol_id: Option<&str>,
+		consensus_engine: Option<&str>,
 	) -> Self
 	{
 		let spec = ChainSpecFile {
@@ -160,6 +166,7 @@ impl<G: RuntimeGenesis> ChainSpec<G> {
 			boot_nodes: boot_nodes,
 			telemetry_url: telemetry_url.map(str::to_owned),
 			protocol_id: protocol_id.map(str::to_owned),
+			consensus_engine: consensus_engine.map(str::to_owned),
 		};
 		ChainSpec {
 			spec,