DataEngineTracker is a simple class that follows all activity in a given Plasma::DataEngine.

Simply add it to your project and then instantiate it with a Plasma::DataEngine* as the first
parameter. This will let you watch sources as they are added, removed and change state. Very
handy to see how a Plasma::DataEngine is being used and behaving, and as such useful for both
DataEngine authors as well as those writing code using DataEngines.
