ZigBee: Enable heuristic dissection of Tunneling cluster payload

ZigBee: Enable heuristic dissection of Tunneling cluster payload

The Smart Energy Tunneling cluster can carry various payloads.
The type of payload is determined when the tunnel is established.
However, we cannot be sure to capture the tunnel establishment and
therefore heuristics are used to determine the payload type.

The IP protocol is added as a heuristic dissector because the
specification allows IP in the tunnel payload. However, the only
real life payload type I am aware of is GBCS messages in
UK Smart Metering (https://smartenergycodecompany.co.uk).

Finally, if a heuristic dissector cannot be found, the Data
dissector is used.

Change-Id: I4942bf00d0d0efe7047db6494cd4f8a9d19c96b6
Reviewed-on: https://code.wireshark.org/review/25181
Petri-Dish: Alexis La Goutte <alexis.lagoutte@gmail.com>
Tested-by: Petri Dish Buildbot
Reviewed-by: Martin Boye Petersen <martinboyepetersen@gmail.com>
Reviewed-by: Anders Broman <a.broman58@gmail.com>