MQTT and config simplification

[yatharthranjan]

• Support for MQTT in the python module (#29 )
• better config management
• Also add explicit stopping of services
• MQTT support for data consumption kotlin module

closes #21

Still needs work to improve the management of the configs. Possibly the gsoc contributor can take this up.

Things to do:

• [x] Encapsulate all the config of a single sensor as a class
• [x] The above class should also hold any dynamically instantiated objects like the Consumers + Converters.
• [x] A higher level class that includes the list of the above sensor configs. Only pass this class wherever sensors are needed.