Containerize worker nodes

[hdoupe]

This PR uses Docker to containerize the worker nodes. This gives the following advantages:

1. Only have to build the updated environment once! This means that you don't have to build the environment locally for local developement and ten more times for all of the worker nodes.
2. Local development environment is very close to identical to the production environment.
3. We can start to phase in container orchestration software which will make deployments faster and safer and allows us to scale the number of worker nodes as needed.

To-do list for remaining items coming shortly...

[hdoupe]

Docker setup documentation will be addressed next week in a follow up PR.