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/Cargo.toml

@@ -9,6 +9,7 @@ build = "build.rs"
 [dependencies]
 parachain = { package = "polkadot-parachain", path = "../../", default-features = false, features = [ "wasm-api" ] }
 codec = { package = "parity-scale-codec", version = "1.3.0", default-features = false, features = ["derive"] }
+sp-std = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
 tiny-keccak = "1.5.0"
 dlmalloc = { version = "0.1.3", features = [ "global" ] }
 
@@ -20,4 +21,7 @@ wasm-builder-runner = { package = "substrate-wasm-builder-runner", version = "1.
 
 [features]
 default = [ "std" ]
-std = ["parachain/std"]
+std = [
+	"parachain/std",
+	"sp-std/std",
+]