Look up dataengines in kf5/plasma/dataengines

This changes the path where to find dataengines to the
subdirectory-per-servicetype setup.

Note: You'll need to update and reinstall kde-workspace/plasma, to
install the dataengines into the new path.

CCMAIL:plasma-devel@kde.org

src/plasma/pluginloader.cpp

@@ -117,7 +117,7 @@ QString PluginLoaderPrivate::parentAppConstraint(const QString &parentApp)
 PluginLoader::PluginLoader()
     : d(new PluginLoaderPrivate)
 {
-    d->pluginDir = "kf5";
+    d->pluginDir = "kf5/plasma/dataengine";
     d->isDefaultLoader = false;
 }