Enabling CORS in GeoServer 2.8.2 or how to use JSONP in GeoServer?

I want to identify number of layers in to workspace in GeoServer for that I am using below REST API:

http://admin:geoserver@localhost:8080/geoserver/rest/workspaces/gisc/featuretypes.json?callback=?

My application is running on IIS so I am using JSONP. I have enabled JSONP in GeoServer but I can not get output, always getting error "**Uncaught SyntaxError: Unexpected token :"

I tried:

var url  = "http://admin:geoserver@localhost:8080/geoserver/rest/workspaces/gisc/featuretypes.json?callback=?";

$.ajax({
 type: 'GET',
 url: url,

 async: false,
    jsonpCallback: 'parseResponse', 
    contentType: "application/json",
    dataType: 'jsonp',  
    success: function(data)
    {
        console.log(data);
    },
    error: function (e)
    {

        console.log(e);
    }
 });

I have also tried another combination but it won't work I am always getting same error.

I have also tried to enable CORS in Jetty using "org\mortbay\servlets\CrossOriginFilter.class" it works with WMS and WFS but won't work with featuretypes.json.