Simplify SODA configuration to enable run-on-demand

The SODA service is complete in terms of functionality. Now we can review and simplify the configurability of the Docker container. Currently the container requires a configuration file to set up directories and other settings. We could change SODA so that it is fully configurable via environment variables (no need for the config file mapping). This change will also allow the SODA service to be launched on demand (simply by running "docker run <params>" without any need of config preparation) as an alternative to running it as a service.