A Transaction (and its subsequent scripts) do not carry any network
specific information in the Bitcoin protocol.
Therefore they can not (without further context) produce the network
specific constants for the generation of the base58 Addresses.
As TransactionOut.address is used heavily throughout Wallet and other
areas of the library, this could not be entirely removed without a large
number of changes.
For now, TransactionOut.address is only defined in the case of
Tx.addOutput being used directly:
Transaction.addOutput(address, value)
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