Jersey Client DigestAuthenticator: qop=auth-int support added

Hi, 
I recently needed the integrity check mechanism for Digest Auth, so I implemented it. Now both auth and auth-int are supported.
I also added a few more test cases.
Please review. I am not 100% sure whether my method for looking up the MessageBodyWriter in DigestAuthenticator.java is the most optimal solution possible.
Stefan Katerkamp
why it does not work? This mechanism is used internally in Jersey, so it should work here too. See the usage in WriterInterceptorExecutor.