Readers rejoice

Added the ability to download books from the server. This means if you click on the new read icon for a book it'll download it. If you're using PDFs then you'll be able to read it right there in the browser.

There's also a small bugfix included to allow more files to be uploaded in one batch. There was a timeout of 3 seconds which has been increased to 5 minutes - this should be plenty of time for most use cases.