Fix contract_count not inserted in db

basicswap/interface_nmc.py

@@ -0,0 +1,12 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+# Copyright (c) 2020 tecnovert
+# Distributed under the MIT software license, see the accompanying
+# file LICENSE or http://www.opensource.org/licenses/mit-license.php.
+
+from .interface_btc import BTCInterface
+
+
+class NMCInterface(BTCInterface):
+    pass