added support for Windows Phone 8.1 (IE11)

This fixes a lot of quirks when using Windows Phone 8.1 (apparently setMetadata has issues on mobile IE11). Also fixes an issue with Cordova 3.x on Windows Phone, where passing image URLs in quotation marks (e.g. "http://example.com/abc.jpg" instead of http://example.com/abc.jpg) throws an exception.