export keys: remove unused dependencies `bitcoinjs-lib` and `util/stealth`.
export keys: remove unused dependencies `bitcoinjs-lib` and `util/stealth`.

This may be undesired: former can (probably) be used to change the
export format, latter can (perhaps) be used to export master sectet and
known keys with history.

CryptArc/darkwallet,darkwallet/darkwallet,darkwallet/darkwallet,salmion/dashwallet,CryptArc/darkwallet,salmion/dashwallet