Adding docker support

[slaterx]

This PR applies changes in the configuration JSON file to accept environment variables. There's the new following elements:

• A Dockerfile which sets the container environment, compiles the binaries and sets permission on the scripts
• An init script that creates on runtime a bot-config.json, based on environment variables (and falling back to defaults if a var is not set)
• Steps for running the project as a docker container.

Also, we added another default path for the application to search for its configuration.

Thus, one could package and/or use it it as a binary application with the sample config (by copying the sample JSON file) in a machine, or as either a plain docker container, a k8s container or an OpenShift element with the new templated configuration (by setting the environment variables).

[0x111]

Thanks for the PR, I see the builds went through, I will take a look at this in the coming days, but if you say this can be also used as a docker container, then I have nothing against it.

[0x111]

Thank you @slaterx looks fine. I've just modified the readme a bit to include docker hub option too. This way it will be easier for the others to also use it.