MQTT-SN Version 2 Codecs

Hi,
Per the last TC meeting, this is an update RE: the status of the first v2 implementation attempt. At present, this is the codecs only (the gateway runtime isn't quite ready, i'm still yet to implement auth in the runtime - estimate mid Jan' for this).
https://github.com/simon622/mqtt-sn/tree/master/mqtt-sn-codec
Please feel free to have a look and play. I have hooked in some basic tests but these will need padding out in the new year.
Best wishes,
Simon.