Allow image padding

It would be awesome if we could break out of the bounds of the original image and add padding where necessary to show the full image.

With reference to the attached image, we want to show the whole t-shirt, but because the uploaded image's content is so hard up against the edges the maximum possible size is being cut off.

I guess this would involve modifying jcrop, adding a modifiable background colour, and adding padding to the cropping area depending on the ratio defined.