Added support for using a bundle file in place of a base64 string.

Following the base64 prefix structure, I added new  "bundleFile" prefix. In place of the base64 data, you need to write the name of file in the bundle and it will return it's contents as body data. Ex:

```
.*\.jpg
200
Content-Type: image/jpeg;bundleFile

imageA.jpg
```

 It's working properly for testing using the simulator.