Add a server side sample for symfony2 

I experienced an issue where onComplete callback not fired when upload is finished if using Symfony2 framework. This is related to an old issue here: http://code.google.com/p/jpegcam/issues/detail?id=15

I found that it is related to setting the appropriate response content-type.

Thus, I decided to make a working sample for Symfony2 framework. This should be applicable to other PHP framework too.