Clarity and LinkamStage do not implement required abstract methods

[iandobbie]

David's latest updates have broken the Clarity device. On startup it generates an error:

TypeError: Can't instantiate abstract class Clarity with abstract methods _on_shutdown, initialize

[carandraug]

The mentioned changes that broke the Clarity is commit 83f1256 . Seems like our ABCs never worked in Python 3. That change fixed it so all devices that didn't implement the Device abstract methods are now failing like they should. I went now through the devices and seems to me that the LinkamStage also does not implement the initialize and _on_shutdown methods.

[carandraug]

I have now fixed the issue for the LinkamStage in c0a7073 . I went through the other classes and seems like they all have the required methods. Closing as fixed.