Make new file notification not rely on buttons being visible
As per gnome-shell#2059 (comment 1640706):
The design for notifications kinda expects there to be an application (or utility) window that can be brought up by clicking the notification, and that window would present the same actions in context.
For that to work, we should show uploads to the computer as they happen (fixing #32 and #30), and offer a choice about downloads both in the notification, and in the app window.