Response string charset option

The XML response of the web service I need is encoded in ISO-8859-1. I experienced false characters with no way for me to handle or convert the response string properly since UTF-8 is hardcoded. The charset has to be set when the response string is built.

I simply added a class variable for the charset to the AsyncHttpResponseHandler. The default is still UTF-8, but now there's an option to set the charset via a setter. I did not add another constructor with a charset-string as a parameter (yet?) to keep it simple.