We now allow you to download files by right-clicking a link and then
choosing "Download".
All files are currently saved to the standard downloads location that
we get from Core::StandardPaths::downloads_directory().
In the future, we'll probably want to come up with a more restrictive
way of doing the "write to disk" portion of this.
We should also improve the ProtocolServer to allow streaming of data
instead of writing everything in one big go.
At the moment, I'm just pretty happy with this GUI. :^)
