Change $cropURL in InputfieldCropImage.module so it isn't relative

Solves "Unrecognized path" problem when cropping an image as a result of editing pages from a different location other than from the default "/processwire/page/" location. (Further explanation: I created a module that lists pages with a specific template, located at "/processwire/teachers/".  When I go to edit a page from there and crop an image from there, it was taking me to "/processwire/teachers/image-crop/?filename..." which resulted in an "Unrecognized path" error.)