New port: net/nethogs

NetHogs is a small 'net top' tool. Instead of breaking the traffic down
per protocol or per subnet, like most tools do, it groups bandwidth by
process.

WWW: https://github.com/raboof/nethogs

PR: 213109
Submitted by: anastasios@mageirias.com
Approved by: lme (mentor)
Differential Revision: https://reviews.freebsd.org/D9892