Transaction: remove TxIn/TxOut exports
Transaction: restrict TxIn input parameters

TransactionIn is only used by Transaction.prototype.addInput and the
Transaction constructor.
It is therefore safe to restrict these input parameters.
Transaction: use TxIn/TxOut consistently
Transaction: extract DEFAULT_SEQUENCE constant
Transaction: rename hashTransactionForSignature to hashForSignature
Transaction: rename (de)serialize to [to/from]Buffer
Address: consistent json formatting
Address/Script: consistent function ordering
Script: use PubKey objects not prebuilt Buffers
syncscript: general cleanup