Implement basic upward & downward messages (#118)

* Start by replacing branch names and set `DownwardMessage`

* Add the upward-message crate

* Add Kusama & Polkadot

* More work on getting the upward messages working

* Fix build

* Begin to integrate it into the test Parachain

* Update

* Make everything compile again

* Switch to westend and print parachain account on startup

* Use MultiSignature etc

* Fix validate block

* Some downward messages work

* Update git reference

* More downward messages integration

* Update test runtime for downward messages

* Enable downward message handler and withdraw send tokens

* Add some docs

* Begin to implement simple XCMP

* More work

* Fixes and make parachain id configurable

* Make parachain ID be part of the genesis

* Finishing the XCMP message demo

* Update and fixes tests

* Update branch

cumulus/primitives/Cargo.toml

@@ -18,6 +18,9 @@ polkadot-primitives = { git = "https://github.com/paritytech/polkadot", branch =
 codec = { package = "parity-scale-codec", version = "1.0.5", default-features = false, features = [ "derive" ] }
 impl-trait-for-tuples = "0.1.3"
 
+# Polkadot dependencies
+polkadot-core-primitives = { git = "https://github.com/paritytech/polkadot", branch = "cumulus-branch", default-features = false }
+
 [features]
 default = [ "std" ]
 std = [
@@ -26,5 +29,6 @@ std = [
 	"polkadot-primitives/std",
 	"polkadot-parachain/std",
 	"sp-inherents/std",
+	"polkadot-core-primitives/std",
 	"sp-runtime/std",
 ]