Tombstone support

[shish]

When an image is deleted, add a database entry; if somebody tries to view that image, show the tombstone instead of the default 404 page

[AstroAntics]

Did you get the idea from Newgrounds? I remember they had a tombstone there too. I don't remember if it had a reason or not to go along with it. Do you think there's any benefit to showing the user why the image was deleted?

I personally believe that there would be (i.e. "banned hash", "poor quality", "TOS", etc), but I can see the flip-side of the argument as well. Some other sites already do this anyway, and display why an image was deleted if you go over it.

edit: Since the "tombstone" itself is a database entry, the comment could be stored in a varchar/smalltext column in case the site needs to bring it up.

[shish]

I got the idea from end-user requests, no idea where they got it from - there are pros and cons, but if it's an option that site owners can choose to enable or disable for their own sites then it seems sensible to add it :3