CAPWAP: Split CAPWAP Control and Data in 2 different protocol

Avoid to have 2 CAPWAP in Decode as (and more easy to use too...)

Change-Id: I3a332e9b4b069b9215c38b5c08872bd07ac4c2c3
Reviewed-on: https://code.wireshark.org/review/3954
Reviewed-by: Jeff Morriss <jeff.morriss.ws@gmail.com>
Reviewed-by: Anders Broman <a.broman58@gmail.com>