Beta Backports (#2396)

* Removing extras data from retracted blocks. (#2375)

* Removing extras data from retracted blocks.

* Adding a test case

Conflicts:
	ethcore/src/blockchain/blockchain.rs

* Fixing transaction queue

Conflicts:
	ethcore/src/miner/transaction_queue.rs

* Prioritizing re-imported transactions (#2372)

* Prioritizing re-imported transactions

* Fixing compilation on beta

Conflicts:
	Cargo.lock
	ethcore/src/client/client.rs
	ethcore/src/miner/transaction_queue.rs

* Post-merge fixes