Don't fork D-Bus into the background.
Removed two unused imports.
All services and targets now have to inherit from either Service or Target.
Make getting the name of a service or target easier.
Service (in ServicesAndTargets) now is a dummy service.
Merge recent changes from "both".
Using __str__ of services and targets.

And I fixed a bug in check_targets_are_reached that I hadn't noticed before.