add Jcrop to image upload attributes

http://deepliquid.com/projects/Jcrop/demos.php?demo=advanced

Using the size contraints setup when creating image attributes, it would be great to allow clients to actually be able to resize normal dimension images directly in the software, rather than requiring them to have access to some sort of image editing software.

Basic croping could be enabled by default if no dimensions are given, but if height/width constraints are added, aspect ratio and maxSize settings come into play