remove network pause

Add optional parameter to Worker constructor for sleep period.
fix client repeat-disconnect loop.
removed resolver from getifaddr dance (not reqd) and updated getifaddr code (needs windowz/linux testing).
don't accept new connections if listenport bind fails (possible due to OS firewall settings).
only use upnp w/ipv4 addresses.
re: disconnect loop. Looks like ethhost session isn't deallocating once stopped. Thinking UI might have shared_ptr. For now, letting dealloc/quit continue as long as isOpen returns false -- maybe okay since network will be halted. Also, it maybe possible the issue is due to network thread not running after disconnect so packets aren't tx/rx to kill peer -- either way, it's possible remote end doesn't ack disconnect and timeout/force-close-dealloc is required, so will need more attention later.
Nice! This code is going away though, so I'll catch this in the next refactor. That is, adding ipv6 and only binding addresses which are appropriate for the network configuration. Private addresses will not be bound unless private networking is enabled, local addresses will not be bound, and this code will be abstracted into a static network method which is passed a list of interface addresses.