output of decrypting message is base64

`com/radixdlt/client/application/translate/data/DecryptedMessage.java`:75

```
	@Override
	public String toString() {
		return timestamp + " " + from + " -> " + to + ": " + encryptionState + " " + Base64.toBase64String(data);
	}
```

Why not just `+ String(data)`?
When you subscribe to result of sending a message, it's very confusing.

 