S allius/issue217 (#229)

* move config.py into a sub directory cnf

* adapt unit test

* split config class

- use depency injection to get config

* increase test coverage

app/tests/test_modbus_tcp.py

@@ -6,7 +6,7 @@ from aiomqtt import MqttCodeError
 from mock import patch
 from enum import Enum
 from singleton import Singleton
-from config import Config
+from cnf.config import Config
 from infos import Infos
 from mqtt import Mqtt
 from inverter_base import InverterBase