State cache and other performance optimizations (#1345)

* State caching

* Better code caching

* Execution optimizaton

* More optimizations

* Updated wasmi

* Caching test

* Style

* Style

* Reverted some minor changes

* Style and typos

* Style and typos

* Removed panics on missing memory

substrate/core/client/src/in_mem.rs

@@ -448,7 +448,7 @@ where
 		self.pending_authorities = Some(authorities);
 	}
 
-	fn update_storage(&mut self, update: <InMemory<H> as StateBackend<H>>::Transaction) -> error::Result<()> {
+	fn update_db_storage(&mut self, update: <InMemory<H> as StateBackend<H>>::Transaction) -> error::Result<()> {
 		self.new_state = Some(self.old_state.update(update));
 		Ok(())
 	}
@@ -491,6 +491,10 @@ where
 		self.aux = Some(ops.into_iter().collect());
 		Ok(())
 	}
+
+	fn update_storage(&mut self, _update: Vec<(Vec<u8>, Option<Vec<u8>>)>) -> error::Result<()> {
+		Ok(())
+	}
 }
 
 /// In-memory backend. Keeps all states and blocks in memory. Useful for testing.