Distros often have additional rules in the their iptabvles 'filter' table
that do things like:
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
docker, for example, gets around this by adding explicit rules to the filter
table's FORWARD chain to allow traffic from the docker0 interface. Do that
for a given host interface too, as a chained plugin.
- start list of linux_only plugins; ignore them when testing on Windows
- Isolate linux-only code by filename suffix
- Remove stub (NotImplemented) functions
- other misc. fixes for Windows compatibility
