Filedrop should not assume you send back JSON formatted string

[bertoost]

Filedrop is great! Only (at least) the finish callback does the $.parseJSON already. I think it's not up to Filedrop to assume JSON is being returned from the ajax request. It should just pass the responseText without the parseJSON() and not assume it's a JSON format. This should be up to the end user (we! the developers! hehe).