speedup Validation::Tx#total_in and total_out
add coinbase_maturity and retarget_interval in the network config
allow to set Block#bip34_block_height aswell
add Tx#is_coinbase?
allow Script#to_pubkey_script_sig without pubkey (for pay-to-pubkey and pay-to-pubkey-hash)

  todo: maybe rename it because its name is wrong and confusing
add hashing opcodes test script
rescue script parsing but still survive serialization roundtrips

  tx ebc9fa1196a59e192352d76c0f6e73167046b9d37b8302b6bb6968dfd279b767 has hand crafted bad op_pushdata's which are but never run by bitcoind until someone tries to redeem them. for serialization its a different story and we need them to survive serialization roundtrips in order to generate the exact right payload from a tx in json format again.