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/core/network/src/specialization.rs

@@ -25,9 +25,6 @@ pub trait Specialization<B: BlockT>: Send + Sync + 'static {
 	/// Get the current specialization-status.
 	fn status(&self) -> Vec<u8>;
 
-	/// Called on start-up.
-	fn on_start(&mut self) { }
-
 	/// Called when a peer successfully handshakes.
 	fn on_connect(&mut self, ctx: &mut Context<B>, who: NodeIndex, status: ::message::Status<B>);