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/state-machine/src/lib.rs

@@ -64,6 +64,9 @@ pub use overlayed_changes::OverlayedChanges;
 pub use trie_backend_essence::Storage;
 pub use trie_backend::TrieBackend;
 
+/// Default num of pages for the heap
+const DEFAULT_HEAP_PAGES :u64 = 1024;
+
 /// State Machine Error bound.
 ///
 /// This should reflect WASM error type bound for future compatibility.
@@ -291,7 +294,7 @@ where
 		.to_vec();
 
 	let heap_pages = try_read_overlay_value(overlay, backend, well_known_keys::HEAP_PAGES)?
-		.and_then(|v| u64::decode(&mut &v[..])).unwrap_or(8) as usize;
+		.and_then(|v| u64::decode(&mut &v[..])).unwrap_or(DEFAULT_HEAP_PAGES) as usize;
 
 	// read changes trie configuration. The reason why we're doing it here instead of the
 	// `OverlayedChanges` constructor is that we need proofs for this read as a part of