Downward & Upward messages (#1266)

* Downward messages, the front-end.

* Move types around to make them accessible from Parachains

* Fix compilation

* Fix branch

* Make it compile for Cumulus

* Update the branch names

* Add default generic parameter

* Implement `Partialeq`

* Move upward messages into the `ValidationResult`

* Support disabling of the runtime api

* Update branch

* Adds support for handling downward messages

* Implement sending XCMP messages as up/downward messages

* service: update to latest ServiceBuilder changes

* Make it compile

* Initial commit

Forked at: ef2aa428d7
Parent branch: origin/master

* Update substrate branch to cecton-update-polkadot-substrate

* Update substrate & polkadot to cumulus-branch

* Reset branch

* Update primitives/src/parachain.rs

Co-authored-by: Robert Habermeier <rphmeier@gmail.com>

* Update runtime/common/src/parachains.rs

Co-authored-by: Robert Habermeier <rphmeier@gmail.com>

* Update runtime/common/src/parachains.rs

Co-authored-by: Robert Habermeier <rphmeier@gmail.com>

* Minor fixes

* Fix wasm build

Co-authored-by: Gav Wood <gavin@parity.io>
Co-authored-by: André Silva <andre.beat@gmail.com>
Co-authored-by: Cecile Tonglet <cecile.tonglet@cecton.com>
Co-authored-by: Robert Habermeier <rphmeier@gmail.com>

polkadot/parachain/test-parachains/adder/collator/src/main.rs

@@ -23,7 +23,7 @@ use adder::{HeadData as AdderHead, BlockData as AdderBody};
 use sp_core::Pair;
 use codec::{Encode, Decode};
 use primitives::{
-	Hash,
+	Hash, DownwardMessage,
 	parachain::{HeadData, BlockData, Id as ParaId, LocalValidationData, GlobalValidationSchedule},
 };
 use collator::{ParachainContext, Network, BuildParachainContext, Cli, SubstrateCli};
@@ -60,6 +60,7 @@ impl ParachainContext for AdderContext {
 		_relay_parent: Hash,
 		_global_validation: GlobalValidationSchedule,
 		local_validation: LocalValidationData,
+		_: Vec<DownwardMessage>,
 	) -> Self::ProduceCandidate
 	{
 		let adder_head = match AdderHead::decode(&mut &local_validation.parent_head.0[..]).ok() {