adds an eject icon as a second column in the device notifier only for mounted devices: it makes more intuitive to unmount a gived external disk.

the look at the moment is:
<a href="/issues/2008-03-16/files/devicenotifier_eject.png">http://www.notmart.org/misc/article_images/devicenotifier_eject.png</a>;

it's not the final one, the unification with kickoff menu aspect is in the works