#15 Canceling update doesn't really cancel

[Sklett]

Although there isn't a cancel button I was able to click the close button ([x]) on the update progress window. This closed the window however the queued updates continued to happen in the background. Somewhere in the middle of this I deleted the version folder the updates were being saved to. As the updates kept being downloaded it eventually tried to start my application and this of course threw exceptions because required assemblies were missing.

I think the progress dialog should expose a Cancel button (with confirmation) to allow a user to abort an update.