Add availability statistics service and a simple strategy

Strategy: Simply Choose By Statistics

shadowsocks-csharp/View/MenuViewController.cs

@@ -29,6 +29,7 @@ namespace Shadowsocks.View
         private MenuItem enableItem;
         private MenuItem modeItem;
         private MenuItem AutoStartupItem;
+        private MenuItem AvailabilityStatistics;
         private MenuItem ShareOverLANItem;
         private MenuItem SeperatorItem;
         private MenuItem ConfigItem;
@@ -177,6 +178,7 @@ namespace Shadowsocks.View
                 }),
                 new MenuItem("-"),
                 this.AutoStartupItem = CreateMenuItem("Start on Boot", new EventHandler(this.AutoStartupItem_Click)),
+                this.AvailabilityStatistics = CreateMenuItem("Availability Statistics", new EventHandler(this.AvailabilityStatisticsItem_Click)),
                 this.ShareOverLANItem = CreateMenuItem("Allow Clients from LAN", new EventHandler(this.ShareOverLANItem_Click)),
                 new MenuItem("-"),
                 CreateMenuItem("Show Logs...", new EventHandler(this.ShowLogItem_Click)),
@@ -260,6 +262,7 @@ namespace Shadowsocks.View
             PACModeItem.Checked = !config.global;
             ShareOverLANItem.Checked = config.shareOverLan;
             AutoStartupItem.Checked = AutoStartup.Check();
+            AvailabilityStatistics.Checked = config.availabilityStatistics;
             onlinePACItem.Checked = onlinePACItem.Enabled && config.useOnlinePac;
             localPACItem.Checked = !onlinePACItem.Checked;
             UpdatePACItemsEnabledStatus();
@@ -524,6 +527,11 @@ namespace Shadowsocks.View
 			}
 		}
 
+		private void AvailabilityStatisticsItem_Click(object sender, EventArgs e) {
+			AvailabilityStatistics.Checked = !AvailabilityStatistics.Checked;
+            controller.ToggleAvailabilityStatistics(AvailabilityStatistics.Checked);
+		}
+
         private void LocalPACItem_Click(object sender, EventArgs e)
         {
             if (!localPACItem.Checked)