Systemd unit to start and stop Docker containers

Summary:
We currently have Docker containers without autostart functionality.

A systemd unit could be created to start and stop them, with Docker service as dependency.

Fixes T467.

Test Plan: Test the units on Dwellers.

Reviewers: dereckson

Subscribers: ledesillusionniste, replicatorbe, dereckson, Kaliiixx

Projects: Nasqueron Docker deployment squad

Maniphest Tasks: T467

Differential Revision: http://devcentral.nasqueron.org/D20