Add support for Redactor's file and image upload functionalities (and small fix)

Adds 3 file and image upload actions ('fileUpload', 'imageUpload', 'imageList') which can be used to support Redactor's file and image upload functionalities (contents of readme.md where modified to add instructions).

Also, forces $.redactor() to wait until the DOM is ready, making sure the function is loaded and ready to be used, so it's not called before the Redactor's javascript files are interpreted by the browser (wich results in a fatal error depending on the browser).