Adjust Dockerfiles for best practices

@zhengyal, we figured a PR would be the fastest way to discuss improvements to the Official Image Dockerfiles.

I moved the `apt-get update` and `install` to the same `RUN` line to help with cache busting and then we can add the `rm` to the `RUN` and save a little space ([docs.docker](https://docs.docker.com/articles/dockerfile_best-practices/#run)).

I added the `--verbose` flag to simplify the `CMD` and make so it only needs one process as it will now run in the foreground ([docs.docker](https://docs.docker.com/articles/dockerfile_best-practices/#run-only-one-process-per-container)).