Allow resizing of "Add Torrent" window

[HotBlack77]

Pretty simple the add torrent window which appears when you click on a torrent fil or magnet link is not resizaable (windows, relase 1.3.0). In many cases this is not a problem, but sometimes you have a torrent file with a huge number of files with long file names and if you want to only select specific files you end up having to scroll both up and down and left and right, which is a bit of a pain.