default to "localhost:port" and not "":port

Windows doesn't handle empty addresses the way unix-like OSs do.

config/config.go

@@ -149,21 +149,21 @@ var DefaultConfig = Config{
 	},
 
 	APIConfig: APIConfig{
-		ListenAddr:     ":6880",
+		ListenAddr:     "localhost:6880",
 		RequestTimeout: Duration{10 * time.Second},
 		ReadTimeout:    Duration{10 * time.Second},
 		WriteTimeout:   Duration{10 * time.Second},
 	},
 
 	HTTPConfig: HTTPConfig{
-		ListenAddr:     ":6881",
+		ListenAddr:     "localhost:6881",
 		RequestTimeout: Duration{10 * time.Second},
 		ReadTimeout:    Duration{10 * time.Second},
 		WriteTimeout:   Duration{10 * time.Second},
 	},
 
 	UDPConfig: UDPConfig{
-		ListenAddr: ":6882",
+		ListenAddr: "localhost:6882",
 	},
 
 	DriverConfig: DriverConfig{

example_config.json

@@ -15,13 +15,13 @@
   "respectAF": false,
   "clientWhitelistEnabled": false,
   "clientWhitelist": ["OP1011"],
-  "apiListenAddr": ":6880",
+  "apiListenAddr": "localhost:6880",
   "apiRequestTimeout": "4s",
   "apiReadTimeout": "4s",
   "apiWriteTimeout": "4s",
   "apiListenLimit": 0,
-  "udpListenAddr": ":6881",
-  "httpListenAddr": ":6881",
+  "udpListenAddr": "localhost:6881",
+  "httpListenAddr": "localhost:6881",
   "httpRequestTimeout": "4s",
   "httpReadTimeout": "4s",
   "httpWriteTimeout": "4s",