Add new port: sysutils/powermon

Powermon is a small utility that reads the CPU internal power counters,
calculates the current power consumption and displays it together with
some nice statistics on an interactive curses interface.

All Intel CPUs starting with Sandy Bridge are supported. Older Intel
CPUs and CPUs from other vendors don't expose the necessary performance
counters. Additionally some server CPUs like those based on Haswell and
Broadwell do not provide the necessary data.

WWW: https://github.com/Yamagi/powermon

PR: 220450
Submitted by: yamagi@yamagi.org
Sponsored by: Essen Hackathon 2017