streamline docker build

To use docker currently:

1. install amp packager from github
2. build docker image (which in turn installs amp packager from github again within the container)

Effectively, the amp packager is fetched twice. Can streamline this in 2 different ways:

1. Use COPY to copy in the amppackager code from local into container (instead of RUN go get)
2. Build and upload docker image into registry where developers can grab it.

Start by inspecting the Docker build configuration and the current RUN go get step to understand where the amppackager is fetched locally and inside the container. Decide whether the intended outcome is copying local amppackager code or publishing an image to a registry, then verify that the Docker build no longer fetches the package twice.

Written by the indexing model from the issue text.