Add daemon service definitions

[maxfischer2781]

Since cobald already provides the daemon runtime, it should also provide the means to run it as a daemon. This means to provide a systemd unit file, sysv init script, and so on.

Note that setup.py should not automatically install a system service, as there may be viable cases to install as user or standalone service.

I suggest different approach; Python packages themselves should stay neutral as possible and do not force any systemd manipulation which imply root priviledges during setup.py run. What happens if user wants to install your package to a virtualenv for development? Instead, I suggest your application ships with a separate script in bin which can do systemd installation: packaging.python.org/en/latest/distributing/#entry-points
[From stackoverflow thread]

See also #10 , inform @mschnepf

[maxfischer2781]

See #30.