Initial log framework

Also:

- Renamed voltha.py to main.py (due to module collision)
- Added logging related dependencies
- Twisted loop
diff --git a/Dockerfile b/Dockerfile
index 11b2251..1a9ecc4 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -36,4 +36,4 @@
 
 # Exposing process and default entry point
 # EXPOSE 8000
-CMD ["python", "voltha/voltha.py"]
+CMD ["python", "voltha/main.py"]