Fix up dockerized build and release build

This is still WIP but I wanted to get this stuff in so that this is reviewed in more bite sized chunks.
Here you can join the grep and awk as well:

```
docker rmi $(docker images | awk '/^<none>/ {print $3}') 2>/dev/null
```

Also, not sure how this behaves in the case the output is empty, will "docker rmi" with no extra parameters handle it badly? If it returns non-zero then it might break the script under set -o errexit...