Add license header

app/lib/blockchain/interfaces/BlockchainOperator.ts

+// Source file from duniter: Crypto-currency software to manage libre currency such as Ğ1
+// Copyright (C) 2018  Cedric Moreau <cem.moreau@gmail.com>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+
 "use strict"
 
 export interface BlockchainOperator {