Now the recovery, which runs at startup, only scans for known
addresses that were generated and recorded by this wallet.
The coming rescanblockchain RPC implementation, which requires the
wallet to be unlocked, does account discovery.
For users don't want to set/manage a passphrase a default passphrase
"passphrase" will be used during wallet creation.
At startup, the wallet tries to unlock itself using the default
passphrase, or a user provided one (using -p).
Users that prefer a passphrase can override the default one at wallet
creation time using -p, or use the walletpassphrase rpc when
the wallet is running. This will prevent the wallet from auto-unlock,
and preserve the lock-by-default behavior.
