Guess file extension based on content-type. When downloading a file, and no path is supplied to store it, guess the file extension using mimetypes and the content-type header. Also supply a unit test for the HotLinkImageForm.

#downloads-add td {
    padding-bottom: 5px;
}

#downloads-add fieldset {
    margin: 1em 0 1em;
    padding: 0.5em;
}