[TIMOB-25764] Windows: Add support for RequestHeaders for ImageViews

A lot of times an image requires requestheaders, like oAuth/basic auth or others before it can be loaded. Right now a workaround is needed to get these images (doing a XHR call to fetch images, then insert it into imageview). However, by adding support for requestheaders to ImageViews a workaround would not be needed anymore. A possible example of implementation:

Ti.UI.createImageView({
    url: 'http://example.com/my_image.png',
    requestHeaders: {
        'Authorization' : 'Bearer myToken'
    }
});