fix(user) Cropping functionality now works with big pictures

Using jCrop with very big image files causes a problem. When a big image is uploaded to the browser and a preview is shown so that the user can crop part of it, the preview will be automatically resized by the browser to fit the screen. This throws off the x,y coordinates and the crop section width and height returned by jCrop. To fix this crop-image.php has to be modified so that the width and height ratio between the original image and the resized image in the browser are calculated. Using this, the true x,y coordinates along with the crop section size can be calculated for the original image and it can then be processed correctly.