Preserve comment, order form, and account strings from the original wallet
transaction. Also set fTimeReceivedIsTxTime and fFromMe fields for consistency
with CWallet::CreateTransaction. The latter two fields don't influence current
wallet behavior, but do record that the transaction originated in the wallet
instead of coming from the network or sendrawtransaction.
This command allows a user to increase the fee on a wallet transaction T, creating a "bumper" transaction B.
T must signal that it is BIP-125 replaceable.
T's change output is decremented to pay the additional fee. (B will not add inputs to T.)
T cannot have any descendant transactions.
Once B bumps T, neither T nor B's outputs can be spent until either T or (more likely) B is mined.
Includes code by @jonasschnelli and @ryanofsky
