Support of draft-ietf-idr-flow-spec-v6 and some cosmetic improvments

Change-Id: Ieaf23c84d67ccdfdcb167afb382c86797bc1cd2b
Reviewed-on: https://code.wireshark.org/review/3006
Reviewed-by: Evan Huus <eapache@gmail.com>
Petri-Dish: Anders Broman <a.broman58@gmail.com>
Reviewed-by: Anders Broman <a.broman58@gmail.com>