Extender Polishing time! The following problems have been adressed:
* Far more correct spacer implementation. This avoids the spacer jumping around while dragging an item. Also adjustSizeHints is now only called once/spacer move.
* Avoid spacer related memleak.
* Only load extenderItems that are actually detached. This way, attached items won't linger around in case of a plasma crash.
* Use utilities-desktop-extra as icon for items with no saved icon (e.g. items where the icon is set using setIcon(QIcon) instead of setIcon(QString)). Sure beats the questionmark.
* Update mask when offscreen extender items are resized when being dragged to avoid screwed up masks (white borders).
* Start the drag only aften being moved a minimum of QApplication::startDragDistance().
* Correct transformation for calls to showDropZone.
* Use the mouse position for positioning items in extenders or panels, the topleft corner for positioning in a desktop containment. This feels the most natural.
* Move items back to the extender they came from when they're dropped into nowhere.
* Some small code style fixes.