Implement fleet unitfile for Kolla containers

The proposed work is to implement fleet unit file for the kolla containers so that Kolla containers can be deployed on CoreOS hosts. The motivation is that CoreOS is shipped with Docker, etcd, and fleet, which provide an ideal environment for microservice-style DevOps for managing OpenStack containers. The initial plan is
1. Detailed spec file, coreos-deployment.md, which defines the reference architecture and service names in etcd, and more.
2. unitfile for containers
3. wrapper scripts to deploy the unit file
Later, we will consider multi-node HA deployment and also developing ansible playbooks for the unit files.