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/src/inverter_base.py

@@ -12,7 +12,7 @@ from proxy import Proxy
 from async_stream import StreamPtr
 from async_stream import AsyncStreamClient
 from async_stream import AsyncStreamServer
-from config import Config
+from cnf.config import Config
 from infos import Infos
 
 logger_mqtt = logging.getLogger('mqtt')