apply I18N to traffic chart legend (#636)

Signed-off-by: Syrone Wong <wong.syrone@gmail.com>

shadowsocks-csharp/Data/cn.txt

@@ -62,6 +62,8 @@ Change &Font=设置字体(&F)
 &Top Most=置顶(&T)
 &Show Toolbar=显示工具栏(&S)
 Log Viewer=日志查看器
+Inbound=入站
+Outbound=出站
 
 # QRCode Form
 

shadowsocks-csharp/View/LogForm.cs

@@ -108,6 +108,9 @@ namespace Shadowsocks.View
             TopMostMenuItem.Text = I18N.GetString("&Top Most");
             ShowToolbarMenuItem.Text = I18N.GetString("&Show Toolbar");
             Text = I18N.GetString("Log Viewer");
+            // traffic chart
+            trafficChart.Series["Inbound"].LegendText = I18N.GetString("Inbound");
+            trafficChart.Series["Outbound"].LegendText = I18N.GetString("Outbound");
         }
 
         private void Timer_Tick(object sender, EventArgs e)