End of systemd support

As systemd doesn't follow our Social Contract, we have decided to remove it and use OpenRC as our default init system. The decision means that the Stable v0.1 will be the first and the last version supporting systemd.

To ease the transition, systemd support will remain in the stable repositories for the time being, while we are removing it in the Testing version and creating our OpenRC migration guide. As of Stable v0.2 release, systemd support will be completely removed without further notice.

Further details: