Add the ability to “stack” images in thumbnails and browser Merged

Much like the already existing ability to “stack” variants with only one key image displayed, it would be nice to do the same with bursts, HDR merges, pano stitches and depth composites. Most of the time, the user doesn’t want to see (or scroll through) all the images used to create a merge or panorama, just the key image. Same goes for bursts. Currently there is no way to hide the images.