batadv: Add dissector support for batadv v15

The packet format for batman-adv v15 supports:

 * Complete reordered packet type ids
 * reordered flags
 * type-version-length-value data containers
 * new types for coding packets and unicast transfer of TVLVs
 * dropped packet types for vis, translation table query and roaming
 * reordered packet formats
 * transparent fragmentation of batadv packets

Change-Id: I9e6733f9dd6b54eeecda19cf570599161d28b46e
Signed-off-by: Sven Eckelmann <sven@open-mesh.com>
Signed-off-by: Simon Wunderlich <simon@open-mesh.com>
Reviewed-on: https://code.wireshark.org/review/5175
Petri-Dish: Michael Mann <mmann78@netscape.net>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Michael Mann <mmann78@netscape.net>