Interchain message-passing (#117)

* compute ingress and routing in polkadot runtime

* extract parent candidates from block when beginning consensus

* fetch incoming messages when validating

* fix consensus tests

* parachain wasm execution uses messages

* update parachain tests to check if messages are executed

* abstract out network service to make room for network tests

* skeleton for incoming data fetch

* collate ingress from consensus-gossip

* keep track of validated candidates in the shared-table

* add some shared_table tests for new behavior

* broadcast egress messages on gossip

* test compute_ingress

* move network tests to module folder

* dummy network for consensus-network tests

* make consensus network generic over executor

* test egress broadcast and ingress fetch

* fix test compilation

* address some grumbles

* address grumbles and fix parachain shuffle

* remove broadcast parameter from consensus network trait

polkadot/primitives/src/parachain.rs

@@ -177,7 +177,7 @@ pub struct Collation {
 
 /// Parachain ingress queue message.
 #[derive(PartialEq, Eq, Clone)]
-#[cfg_attr(feature = "std", derive(Serialize, Deserialize, Debug))]
+#[cfg_attr(feature = "std", derive(Serialize, Deserialize, Encode, Decode, Debug))]
 pub struct Message(#[cfg_attr(feature = "std", serde(with="bytes"))] pub Vec<u8>);
 
 /// Consolidated ingress queue data.
@@ -288,6 +288,9 @@ decl_runtime_apis! {
 		fn parachain_head(id: Id) -> Option<Vec<u8>>;
 		/// Get the given parachain's head code blob.
 		fn parachain_code(id: Id) -> Option<Vec<u8>>;
+		/// Get the ingress roots to a specific parachain at a
+		/// block.
+		fn ingress(to: Id) -> Option<Vec<(Id, Hash)>>;
 	}
 }