Added mapping downloadDirectoryWin to browser.download.dir

[danschlet]

Changed preferences for not displaying downloads window (browser.download.manager.showWhenStarting = false), for using custom download directory (browser.download.useDownloadDir = true, browser.download.folderList = 2) and for showing alert when download is finished (independent of duration of download: openDelay = 0 and showAlertInterval = 0). Added MIME type application/attemptdata for files with extension .attemptdata (Moodle offline quiz plugin encrypted quiz results) and download policy saveToDisk = true and alwaysAsk = false Added mapping showReloadWarning to seb.reload.warning