This introduces a lot of duplication between the binary and the
library, but it's okay because this module should only be a temporary
measure until we allow recovery to be handled by the original state
machine.
Also, fix a bug in `xmr_btc::alice::action_generator` caused by the
incorrect assumption that Alice's ability to punish Bob could be
determined before the cancel transaction hits the blockchain.
Anything that needs to be re-exported by this crate from
`curve25519_dalek` can be re-exported from the `monero` module. In
fact, the `Scalar` type was already being re-exported.
