unblock local multicast IPs from linux firewall, to allow SSDP and Bonjour/mDNS to work.
return instead of reject for multicast
linux firewall: s/insert/append, and switch order. it makes much more sense to insert custom chain at start of OUTPUT, then append to that chain.
fix bug with ipv6 blocking (added to wrong chain, so never removed and also it would keep getting added repeatedly)
Merge remote-tracking branch 'refs/remotes/elijah/feature/betterfirewall' into develop