testing/arachsys-containers: new aport

arachsys-containers is a simple implementation of containers for Linux, making secure containers as easy to create and use as a traditional chroot. It comprises three utilities: contain, inject and pseudo.

A typical use case looks like this (very simplified): pseudo is used to bootstrap the container, contain runs the container's init (PID 1) process and supervises it, while inject is used to run a command or shell inside the container.