fix meshnet mode:

* don't default to ipv4 when creating router.info
* add i2p::util::config::GetHost for getting host to use from config
* proper check for no transports in Transports.cpp on startup

RouterContext.cpp

@@ -49,9 +49,7 @@ namespace i2p
 		uint16_t port; i2p::config::GetOption("port", port);
 		if (!port)
 			port = rand () % (30777 - 9111) + 9111; // I2P network ports range
-		std::string host; i2p::config::GetOption("host", host);
-		if (i2p::config::IsDefault("host"))
-			host = "127.0.0.1"; // replace default address with safe value
+		std::string host = i2p::util::config::GetHost();
 		routerInfo.AddSSUAddress  (host.c_str(), port, routerInfo.GetIdentHash ());
 		routerInfo.AddNTCPAddress (host.c_str(), port);
 		routerInfo.SetCaps (i2p::data::RouterInfo::eReachable |