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/tests/lib.rs

@@ -18,16 +18,7 @@ mod adder;
 mod code_upgrader;
 mod wasm_executor;
 
-use parachain::{
-	self, primitives::UpwardMessage, wasm_executor::{Externalities, run_worker},
-};
-
-struct DummyExt;
-impl Externalities for DummyExt {
-	fn post_upward_message(&mut self, _: UpwardMessage) -> Result<(), String> {
-		Ok(())
-	}
-}
+use parachain::wasm_executor::run_worker;
 
 // This is not an actual test, but rather an entry point for out-of process WASM executor.
 // When executing tests the executor spawns currently executing binary, which happens to be test binary.