Align Ansible and Docker deployment configuration

[huard]

Description

The current Dockerfile runs the demo configuration:
CMD ["source activate wps && exec {{ cookiecutter.project_slug }} start -b 0.0.0.0 -c /opt/wps/etc/demo.cfg"]

I suggest we have a sample prod.cfg to show an example of how birds are configured for production environment. Over time, we'll be able to recommend settings reflecting our experience with running operational PyWPS servers.

An open question is which config should the docker CMD target. We could stick with demo as I suspect it might be easier to setup, but we should add comments highlighting the need to define a prod config.