WIP: Make OSD position configurable
The default OSD position will never make everybody happy, so this commit makes it a config option (in kwinrc). I would then put a UI to set it in Workspace Behavior->General Behavior, right under the "Display visual feedback for status changes".
I'm not entirely sure how to access the kwin config from there though, some hints in the right direction would be nice. Alternatively, is it possible to access the Plasma config from KWin? Then it might be good to group possible future OSD options in there, too.