Containerize OpenTripPlanner; run as a service via Docker

[Hector Castro]

Work toward the containerization of OpenTripPlanner such that it can function as a service within the OTP virtual machine. Migrate the existing systemd service configuration such that it uses the Ansible docker_service module.

See: https://github.com/WikiWatershed/model-my-watershed/blob/e70fef2ce907193a853d6f6f2358706a625ffbb8/deployment/ansible/roles/model-my-watershed.rwd/tasks/app.yml#L6-L24