Add setting to disable hotlinking of large image files

[vinothkannans (Vinoth Kannan)]

Very large gifs should be shown as previews

@vinothkannans does the tooltip work now so I can mouse over this kind of random looking generic image placeholder and get a plain English explanation of what happened?

Also go with grey for both icons

I will do both of it on new PR. Also I am waiting for a solution to below problem. Can you @codinghorror or @sam suggess me any way to handle this situation.

I linked large image placeholders to the original external image url. What if the large image is already linked. Should I skip linking with original image url?

If skipped then user can’t see the image at all.