Engine v0.6.1

Add v0.6.1 Dockerfile & prebuild.sh script

Currently the pipeline will fail due to missing AWS keys for access to our s3 bucket used for hosting the source/deps tarballs. @taylor I was hoping you could add these environment vars to our Jenkins build context AWS_ACCESS_KEY_ID AWS_SECRET_ACCESS_KEY - we can provide the values for those env vars in another communication channel. This will allow scripts/prebuild.sh to grab the tarballs from s3, verify the checksum & upload them to nexus for the Dockerfile to ingest.

I also don't have access to this repo - https://dccscr.dsop.io/dsop/dccscr-whitelists/tree/master/anchore - which I think needs to be updated to use the correct base images & tags for v0.6.1. From what I can tell, the greylist files from the 0.6.0 directory will work, but the tags will need to be updated to v0.6.1

Finally, because the enterprise image uses the engine image as a base, the engine pipeline will have to build/push before the enterprise pipeline gets kicked off.

Hopefully that will be enough get this process automated.