Several changes:

- monitoring/requirements.txt: removed garbage on top of file
- monitoring/monitoring_client.py: solved bug in return values of some methods and wrong code in test case
- monitoring/monitoring_server.py: solved bug with instantiation of servicer class
- monitoring/Dockerfile: clarified some arguments in package installation, moved code in container to /var/monitoring, added upgrade of essential python packages, other minor improvements
- monitoring/context_pb2.py: upgraded version since previous has no contextId fields.