Adjust all components to use the QSharedPointer. Aurorae obviously has
to create a QSharedPointer, Shadow holds a QSharedPointer for the
DecorationShadow (advantage: is kept when the Decoration is destroyed),
and the KCM needs to add a property on PreviewItem to get access to the
Shadow. It's no longer a Q_PROPERTY on Decoration and we cannot re-add
it as a dynamic property (cannot be read from QML side).
Following features are supported:
* finds all plugins
** finds all themes for a theme-engine plugin
* renders previews for the plugin/themes
* loads currently used plugin/theme
* saves selected plugin/theme
* triggers config reload in KWin
Following features are currently not supported:
* Search
* Plugin configuration
* GHNS
* Button configuration
