Fixing an issue with .psd files with effects in them.

The issue was that it was downscaling .psd files and saving them as .psd files. Now it saves the temporary downscaled image as a png file, but with the .psd extension. Later stages in the SB publishing steps need the filename to stay the same. ImageIO doesn't actually look at the extension anyway, so it's able to read the files correctly.

The temporary image is deleted in a later step before the publishing is complete.