Adding possibility of websockets configuration

Up to now, websockets configuration was possible for the daemon only,
   this patch passes that information to the client via json file
   produced with the payment request.

lib/wallet.py

@@ -1052,6 +1052,8 @@ class Abstract_Wallet(PrintError):
                 out['request_url'] = os.path.join(baseurl, key)
                 out['URI'] += '&r=' + out['request_url']
                 out['index_url'] = os.path.join(baseurl, 'index.html') + '?id=' + key
+                out['websocket_server'] = config.get('websocket_server', 'localhost')
+                out['websocket_port'] = config.get('websocket_port', 9999)
         return out
 
     def get_request_status(self, key):