New features

fixed bug in base class PluginJobs.
added Tk::DynaMouseWheelBind to AppWindow and bound it to some classes.
revised extension Art. Moved all icon search methods to FreeDesktop::Icons. Added -rawiconpath option.
plugins can now have their own settings page.
the tool bar can now have drop down lists.
removed the Balloon extension. Tk::AppWindow now has a balloon widget by default.