* passing a null or invalid QVariant to DataSource::setData now results in the removal of the entry if it exists
svn path=/trunk/KDE/kdebase/workspace/libs/plasma/; revision=676783
* data sources now signal when the are unused
* listen to the unused signal for sources created on demand via dataSourceRequested
svn path=/trunk/KDE/kdebase/workspace/lib/plasma/; revision=673389
* make DataEngine take a QObject in the connect, making DataVisualization somewhere superfluous. unless it ends up doing something useful soon, DataVisualization as a class will be going away.
svn path=/trunk/KDE/kdebase/workspace/plasma/lib/; revision=667167
* move DataSource::Data to DataEngine::Data; this means consumers of DataEngine have no need to know about DataSource as a class
svn path=/trunk/KDE/kdebase/workspace/plasma/lib/; revision=666756