Consensus Engines Implementation: Aura (#911)

* Generalize BlockImport

 - move ImportBlock, BlockOrigin, ImportResult into shared sr-primitives
 - let Consensus provide  and  traits again
 - update consensus traits to latest development
 - implement traits on client::Client, test_client::TestClient
 - update RHD to use the new import_block API

* Move ImportBlock into consensus-common
* Send import notification in aura tests
* Integrating aura into service
* Make Signatures more generic
* Aura Block Production with the given key
* run aura on the thread pool
* start at exact step start in aura
* Add needed wasm blob, in leiu of better solutions.
* Make API ids consistent with traits and bring upstream for sharing.
* Add decrease_free_balance to Balances module
* Encode `Metadata` once instead of two times
* Bitops include xor
* Upgrade key module.
* Default pages to somewhat bigger.
* Introduce upgrade key into node
* Add `Created` event

substrate/node/runtime/Cargo.toml

@@ -29,6 +29,7 @@ srml-staking = { path = "../../srml/staking" }
 srml-system = { path = "../../srml/system" }
 srml-timestamp = { path = "../../srml/timestamp" }
 srml-treasury = { path = "../../srml/treasury" }
+srml-upgrade-key = { path = "../../srml/upgrade-key" }
 sr-version = { path = "../../core/sr-version" }
 node-primitives = { path = "../primitives" }
 
@@ -53,6 +54,7 @@ std = [
 	"srml-system/std",
 	"srml-timestamp/std",
 	"srml-treasury/std",
+	"srml-upgrade-key/std",
 	"sr-version/std",
 	"node-primitives/std",
 	"serde_derive",