[operator] Document env vars for overriding Jaeger image sources

This is important when running Jaeger on a self-hosted cluster with no direct access to the Docker Hub.

The support for them was added in jaegertracing/jaeger-operator#21, but neither the documentation nor the deployment YAML indicate they exist and what their names are. I had to look at the source code and read Viper documentation to learn that they should be called JAEGER-ALL-IN-ONE-IMAGE, OPENSHIFT-OAUTH-PROXY-IMAGE etc.

Start by locating the documentation and deployment YAML for the Jaeger operator, then compare them with the existing environment-variable support and the Viper naming rules. Document the image override variable names, and update the deployment YAML so both sources show the available overrides.

Written by the indexing model from the issue text.