viewer - basic infinite scroll feature

[FreezingRain]

In 'Settings -> Interface -> Mouse'
add a fourth option to the Mousewheel listbox: "Scroll up/down (infinite scroll)".

This would work exactly like the current "scroll up/down" mousewheel option, except when the bottom of the image is reached, any further scrollwheeling down moves to the next image, and conversely, when scrolled to the very top of an image, the next scrollwheel up moves to the previous image.

On images where no scrolling is possible, as they fit to the screen, scrolling the mousewheel just behaves as current "Previous/next file" mousewheel setting.

Hopefully this would be a pretty simple way to impliment an infinite/unlimited scrolling feature, which is a very comfortable way of reading through a set of comic or manga style images.