Merge branch 'ethersphere-eth.blockpool' into poc8

cmd/ethereum/flags.go

cmd/ethereum/main.go

core/transaction_pool.go

core/types/block.go

eth/backend.go

eth/block_pool.go

eth/block_pool_test.go

eth/error.go

eth/protocol.go

eth/protocol_test.go

eth/test/README.md

eth/test/bootstrap.sh

eth/test/chains/00.chain

eth/test/chains/01.chain

eth/test/chains/02.chain

eth/test/chains/03.chain

eth/test/chains/04.chain

eth/test/mine.sh

eth/test/run.sh

eth/test/tests/00.chain