Fromkeys aftermath

Add Wallet.fromKeys(). Creates a wallet containing a given set of keys. All further keys will be derived from the oldest key.

Add warning about randomly generated keys to Wallet constructor.
How does this paragraph sound? I prefer to use "randomly", because that's what important. Fresh can mean many things.

Creates a new, empty wallet with a randomly chosen seed and no transactions. Make sure to provide for sufficient backup! Any keys will be derived from the seed. If you want to restore a wallet from disk instead, see {@link #loadFromFile}.