NEP2 directly to wallet to avoid double decryption

This will allow going directly from NEP2 to wallet object. If only return Wif have to recall NeoutilsGenerateFrom Wif, which redoes the private key derivation which is costly operation. This should cut time of all wallet switching operations in half

neoutils/nep2/nep2.go

@@ -126,6 +126,54 @@ func NEP2Decrypt(key, passphrase string) (s string, err error) {
 	return privKey.ToWIFC(), nil
 }
 
+func NEP2DecryptToWallet(key, passphrase string) (*Wallet, err error) {
+	encrypted, err := crypto.Base58CheckDecode(key)
+	if err != nil {
+		return s, nil
+	}
+	if err := validateNEP2Format(encrypted); err != nil {
+		return s, err
+	}
+
+	addrHash := encrypted[3:7]
+
+	// Normalize the passphrase according to the NFC standard.
+	phraseNorm := norm.NFC.Bytes([]byte(passphrase))
+	derivedKey, err := scrypt.Key(phraseNorm, addrHash, n, r, p, keyLen)
+	if err != nil {
+		return s, err
+	}
+
+	derivedKey1 := derivedKey[:32]
+	derivedKey2 := derivedKey[32:]
+	encryptedBytes := encrypted[7:]
+
+	decrypted, err := crypto.AESDecrypt(encryptedBytes, derivedKey2)
+	if err != nil {
+		return s, err
+	}
+	privBytes := xor(decrypted, derivedKey1)
+	// Rebuild the private key.
+	var privKey btckey.PrivateKey
+	err = privKey.FromBytes(privBytes)
+	if err != nil {
+		return s, err
+	}
+
+	if !compareAddressHash(&privKey, addrHash) {
+		return s, errors.New("password mismatch")
+	}
+
+	wallet := &Wallet{
+		PublicKey:       privKey.PublicKey.ToBytes(),
+		PrivateKey:      privKey.ToBytes(),
+		Address:         privKey.ToNeoAddress(),
+		WIF:             privKey.ToWIFC(),
+		HashedSignature: privKey.ToNeoSignature(),
+	}
+	return wallet, nil
+}
+
 func compareAddressHash(priv *btckey.PrivateKey, hash []byte) bool {
 	address := priv.ToNeoAddress()
 	addrHash := hashAddress(address)[0:4]