Expose surface addresses in info json

Surface Addresses are the addresses that
the roots report back to you.

This is helpful for trouble shooting.

If you're behind NAT, the source port is different
than what zerotier is bound to.
If the list of surface address ports is larger than the list of
bound addresses, you are probably behind symmetric NAT.

Anways this can be added to later with a more simple
"easy" or "hard" nat computed message somewhere.

service/OneService.cpp

@@ -1560,6 +1560,15 @@ public:
 					}
 					settings["listeningOn"] = boundAddrArray;
 
+					std::vector<InetAddress> surfaceAddrs = _node-> SurfaceAddresses();
+					auto surfaceAddrArray = json::array();
+					for (int i = 0; i < surfaceAddrs.size(); i++) {
+						char ipBuf[64] = { 0 };
+						surfaceAddrs[i].toString(ipBuf);
+						surfaceAddrArray.push_back(ipBuf);
+					}
+					settings["surfaceAddresses"] = surfaceAddrArray;
+
 #ifdef ZT_USE_MINIUPNPC
 					settings["portMappingEnabled"] = OSUtils::jsonBool(settings["portMappingEnabled"],true);
 #else