Tagged transaction queue integration (#893)

* Make the graph generic.

* Adapting pool API for the graph.

* Merge pool & graph.

* Restructure.

* Fix test of transaction pool.

* Get rid of node/transaction-pool.

* Compilation fixes.

* Test7

* Fix compilation of tests.

* Revert runtime changes.

* Add validate_transaction to test-runtime.

* Fix RPC tests.

* Add clearing of the old transactions.

* Trigger pool events.

* Use new queue API.

* Fix wasm build, re-export Hasher.

* No warning if validate transaction fails.

* Get rid of Into<u64> and use As

substrate/core/sr-primitives/src/transaction_validity.rs

@@ -30,8 +30,14 @@ pub type TransactionTag = Vec<u8>;
 
 /// Information on a transaction's validity and, if valid, on how it relates to other transactions.
 #[derive(Clone, PartialEq, Eq, Encode, Decode)]
+#[cfg_attr(feature = "std", derive(Debug))]
 pub enum TransactionValidity {
 	Invalid,
-	Valid(TransactionPriority, Vec<TransactionTag>, Vec<TransactionTag>, TransactionLongevity),
+	Valid(
+		/* priority: */TransactionPriority,
+		/* requires: */Vec<TransactionTag>,
+		/* provides: */Vec<TransactionTag>,
+		/* longevity: */TransactionLongevity
+	),
 	Unknown,
 }