ICMP message-routing gossip (#304)

* core logic for ICMP gossip

* refactor gossip to make more extension friendly

* move files aroun

* extract attestation-gossip logic to its own module

* message validation and broadcast logic

* fix upstream crates' compilation

* add a test

* another test for overlapping

* Some grammar and phrasing tweaks

Co-Authored-By: Luke Schoen <ltfschoen@users.noreply.github.com>

* add since parameter to ingress runtime API

* broadcast out known unrouted message queues

* fix compilation of service and collator

* remove useless index_mapping

* some tests for icmp propagation

* fix decoding bug and test icmp queue validation

* simplify engine-id definition

Co-Authored-By: Sergei Pepyakin <sergei@parity.io>

* address some grumbles

* some cleanup of old circulation code

* give network a handle to extrinsic store on startup

* an honest collator ensures data available as well

* address some grumbles

* add docs; rename the attestation session to "leaf work"

* module docs

* move gossip back to gossip.rs

* clean up and document attestation-gossip a bit

* some more docs on the availability store

* store all outgoing message queues in the availability store

* filter `Extrinsic` out of validation crate

* expunge Extrinsic from network

* expunge Extrinsic from erasure-coding

* expunge Extrinsic from collator

* expunge from adder-collator

* rename ExtrinsicStore to AvailabilityStore everywhere

* annotate and clean up message-routing tests

polkadot/network/Cargo.toml

@@ -18,7 +18,7 @@ sr-primitives = { git = "https://github.com/paritytech/substrate", branch = "pol
 futures = "0.1"
 log = "0.4"
 exit-future = "0.1.4"
+substrate-client = { git = "https://github.com/paritytech/substrate", branch = "polkadot-master" }
 
 [dev-dependencies]
-substrate-client = { git = "https://github.com/paritytech/substrate", branch = "polkadot-master" }
 substrate-keyring = { git = "https://github.com/paritytech/substrate", branch = "polkadot-master" }