net/bone-utils: Add port

This is the [B]ag [O]f [N]etgraph [E]xtensions utilities package is an evolving
set of extra netgraph(4) utilities to simplify using the kernel modules in
net/bone-kmods. Additionally it provides a very simple rc(8) script which
re-names interfaces to match whatever you named them in your ngctl.conf.

At present this module provides the following:

• netgraph rc(8) script that keeps ifconfig(8)/ngctl(8) in agreement on nodes that present a network interface (ng_eiface(4), ng_ether(4), ng_iface(4)).
• jeiface script to create an ng_eiface(4) in a jail giving it the name and optional MAC you request.
• ncpcap(8) connectes to nodes to capture traffic. It is meant to have its output piped to tcpdump(1)
• ngportal(8) is the fast and simple way to connect to vnets using netgraph.

Differential Revision: https://reviews.freebsd.org/D56744