Cleaning Up Dockerfile Layers Per Official Docs

Cleaning Up Dockerfile Layers Per Official Docs

From the official docs:

```
Note: The official Debian and Ubuntu images automatically run apt-get clean, so explicit invocation is not required.
```

Also added ` && rm -rf /var/lib/apt/lists/*` as part of the install line which probably does what was intended (no need to make a new layer).

Added apt-get update to the RUN payload, as it should be part of the same layer.

Both are documented here: https://docs.docker.com/engine/userguide/eng-image/dockerfile_best-practices/