Update README or prod docker image for db initialization

There is a missing step in the README.md for bringing up confighub docker images from Docker Hub: people need to build the confighub db manager and use it to init their db before trying to bring up the docker image and connect to it. This is the "quick solution".

The "better solution" is to have the docker image pull the code, build it, and init the db by itself the first time the confighub docker image comes up.

The "best solution" is to integrate the db manager code into the confighub code. Then the db manager and CH code can be worked upon and built in lock-step, and images can be deployed with all the necessary tools more reasily.

Review README.md and the Docker Hub image startup process to understand the current database initialization steps and the existing db manager. Compare the documented quick solution with the proposed automated and integrated alternatives; clarify which scope is intended before starting. Done should mean users can bring up the image with an initialized database, either through complete instructions or automation.