Changed largestEditorialCrop logic

The current largestEditorialCrop logic (which chooses the largest appropriate image for galleries and lightboxes) had a hole in its logic: any image uploaded at a width of 1024px or 2048px would be filtered out. 

The new logic only filters out images with a width of 1024px/2048px if their aspect ratio matches 4:3, indicating it is an auto-crop.

This makes this cartoon to be lightboxable: http://www.theguardian.com/lifeandstyle/cartoon/2014/dec/06/2

cc @mattosborn