State db random fixes (#802)

* state-db: typo fixes

* use fmt::Result for 'fmt'

* state-db: typo fixes

* state-db: use the same pattern to pass the parameter

* state-db: follow the same style

substrate/srml/balances/src/address.rs

@@ -40,7 +40,7 @@ impl<AccountId, AccountIndex> fmt::Display for Address<AccountId, AccountIndex>
 	AccountId: Member,
 	AccountIndex: Member,
 {
-	fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 		write!(f, "{:?}", self)
 	}
 }