* return an instance of the NullEngine on engine loading failure; this way applets don't have to test for engine existence and can just assume something gets returned
* DataEngine::isValid() in case someone really cares to know whether they have a non-functional engine (e.g. the NullEngine)
svn path=/trunk/KDE/kdebase/workspace/lib/plasma/; revision=670900
#include <plasma/foo.h>
in headers in libplasma. this is important so that they can be used post-install by third party plugins, apps, etc.
also, changed Applet::loadDataEngine to just Applet::dataEngine and make it actually return the data engine; move the applets to using it. safer and fewer LoC
svn path=/trunk/KDE/kdebase/workspace/lib/plasma/; revision=670850
* errorCode is no longer used
* get the debug output in line with similar msgs in plasma
svn path=/trunk/KDE/kdebase/workspace/plasma/lib/; revision=668017
