Add documentation on how to get the upload key

[Rudd-O]

Right now the preferences dialog shows italicized text telling the user to obtain the upload key, but that is of no help. Ideally, in both that dialog box and in the documentation of the project (man pages, README) there would be a hyperlink that takes the user to some page with step-by-step instructions for both Windows and Mac OS X to obtain the key.

[Rudd-O]

Added to the GUI configurator. Still needs to be added to formal documents, with screenshots and the like. It is not enough to just add it to the GUI as it misses the server use case and shortchanges less savvy GUI users.