Show outbound traffic in outbounds table (#1711)

* store outbound traffic in database

* show outbound traffic in outbounds table

* add refresh button

xray/traffic.go

@@ -1,8 +1,9 @@
 package xray
 
 type Traffic struct {
-	IsInbound bool
-	Tag       string
-	Up        int64
-	Down      int64
+	IsInbound  bool
+	IsOutbound bool
+	Tag        string
+	Up         int64
+	Down       int64
 }