Allow images to be copied directly to clipboard by right-clicking, similar to using "Copy Image" in browsers, not just the link.

Good idea

Just realized this is a problem, because the images in the channel view are actually scaled/lower quality thumbnails of the original image, and people probably don't want to copy those. Fetching the original high-quality image takes a while, so I can't download it on demand when someone right-clicks and selects Copy Image. I'll have to think about what to do. Setting to deferred for now.