Basic Authority (#991)

* Firt commit.

* First non-functional but correct implementation of BasicAuthority.

Still needs:
- Sealing infrastructure.

* Punch a hole to give miner access to key store.

* Fix test built.

* Basic version of synchronous mining.

This will seal a block whenever a new transaction comes through.
To be made better we need a timer which will wait for one second after the
last block before sealing a new one - better still would be to cooperatively
interleave blocks with other sealing nodes.

* Add tests.

* Fix minor issues from repotting.

* Address grumbles.

parity/main.rs

@@ -146,7 +146,7 @@ fn execute_client(conf: Configuration) {
 	let client = service.client();
 
 	// Miner
-	let miner = Miner::new(conf.args.flag_force_sealing);
+	let miner = Miner::with_accounts(conf.args.flag_force_sealing, account_service.clone());
 	miner.set_author(conf.author());
 	miner.set_gas_floor_target(conf.gas_floor_target());
 	miner.set_extra_data(conf.extra_data());