add licence headers to more files

electrum/lnutil.py

@@ -1,3 +1,7 @@
+# Copyright (C) 2018 The Electrum developers
+# Distributed under the MIT software license, see the accompanying
+# file LICENCE or http://www.opensource.org/licenses/mit-license.php
+
 from enum import IntFlag, IntEnum
 import json
 from collections import namedtuple