Verification benchmark

Replace non-final transactions in mempool + block assembler won't include such transactions in block

Move overflow checks into separate error type

improvements for import

JSON RPC - getconnectioncount method

JSON RPC - getaddednodeinfo method

hash block and transactions while reading them

Rpc raw continue

few optimizations with Borrow and AsRef

`gettxout` implemented

TransactionOutputBuilder always creates spendable transactions