Bug 1053940 - docker-worker: Encrypted environment variables

One open issue is the management of the gpg keys. Currently they are hard-coded.
Adding it to the runtime is easy enough by adding it at the appropriate spot in bin/worker.js .  I would suggest looking at the other things that are added to the config and then that config is passed to the runtime creator.

Such as: https://github.com/taskcluster/docker-worker/blob/master/bin/worker.js#L166