mq improvements:

- handle RFH structure
- use tvb_reported_length...,
- Add Conversation/Request in row display

Change-Id: I84c5cf3e9479d91b363eb093e71bb6bdf07e8194
Reviewed-on: https://code.wireshark.org/review/3354
Reviewed-by: Anders Broman <a.broman58@gmail.com>