Setting up initial JS for Reportbacks

@weerd Here is my first pass at just setting up the js. I don't remember where we landed on using the prototype pattern for the Reportback.js, but feel free to refactor!
Not sure if you have other plans for this init, but seems like `init` and `imageCropInit` could be combined into just `init`? Not completely sure if you have specific plans as to why you separated them :)