Fix for DatagramSocket.close() issue on Windows and support for graylogServerVersion > 0.9.6

Changed the DatagramSocket construction to use the lookback address to bind on. This fixes an issue on Windows systems where the DatagramSocket.close() takes 3000 ms to unbind when connecting to a non exisitig or disabled graylog server in the same subnet.

Also changed the appender to use the GELF 1.0 format by default.