Prepare for separating the greeter from the daemon

The code we have done so far is just a greeter that will be spawned by
the actual daemon program.
Start writing the daemon

Structuring the daemon code by implementating simple settings and
logger classes.
Simple session management

Use the login1 service to list sessions and receive signals when
sessions are being created or removed.

For more information see:
  http://www.freedesktop.org/wiki/Software/systemd/logind

Issue: #8