Add pcap exporter for packets #1
Description
It's handy to be able to capture traffic for a period of time and analyze it with WireShark (or similar). pcap is a well known file format for capturing packets.
See an example of how to write out these files here
A library such as https://pypi.org/project/pypcapkit/ could be used as well.
Eventually, it would be useful to turn on and off a pcap dumper while the node controller is running, but for a start let's add it as an output option to tarpn-packet-dump. Something like
tarpn-packet-dump /dev/ttyUSB0 19200 --pcap-file packets.pcap