to fix serialization with nested arrays/hashes
(and clients should be notified)
to avoid hitting the db for every duplicate (unsolicited) tx inv
TODO: check order of signatures
for rare cases when sequence is not 0xffffffff.
also, pass in actual hash_type from the script instead of defaulting to 1.
in the new spec fixtures the hash_type is 0. oO while only 1-3 is defined.