Write the concrete implementation of the base classes that will allow DMOD to orchestrate via Docker

[christophertubbs]

blocked by #705

Expected Products

Concrete classes that invoke docker just like how DMOD currently invokes docker. These new classes need to implement the base classes and protocols defined in #705 . No invocation or entrypoint within the Docker implementation of these backend classes should require any knowledge or acknowledgement of docker - that should be encapsulated as implementation details.