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/service.rs

@@ -178,6 +178,12 @@ impl<B: BlockT + 'static, S: Specialization<B>, H: ExHashT> Service<B, S, H> {
 	}
 }
 
+impl<B: BlockT + 'static, S: Specialization<B>, H: ExHashT> ::consensus::SyncOracle for Service<B, S, H> {
+	fn is_major_syncing(&self) -> bool {
+		self.handler.sync().read().status().is_major_syncing()
+	}
+}
+
 impl<B: BlockT + 'static, S: Specialization<B>, H:ExHashT> Drop for Service<B, S, H> {
 	fn drop(&mut self) {
 		self.handler.stop();