Add global hotkey support (#724)

Design:

Use the plain string for both config and hotkey parsing
and make use of KeyConverter, ModifierKeysConverter
to make it more rubust.

Find corresponding label (to display operation result) and callback (to do the real work) based on textbox name. In this case, they should be named as `<Feature-Name><Control-Name>`.

ShowLogsTextBox,
ShowLogsLabel,
ShowLogsCallback.

If this requirement doesn't meet, throw an exception at runtime.

Logic:

How to input keys:
1. put focus in the corresponding textbox
2. press the key combination you want to use
3. when you think it is ready, release all keys
4. the textbox shows your input

How to change keys:
1. put focus in the corresponding textbox
2. press BackSpace to clear content
3. re-input new one

How to deactivate:
1. clear content in the textbox
2. press OK button

Meaning of label color:
- Green: this combination is not occupied by other programs and register successfully
- Yellow: this combination is occupied by other programs and you have to change to another one
- Transparent without color: initial status

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

shadowsocks-csharp/Controller/ShadowsocksController.cs

@@ -374,6 +374,16 @@ namespace Shadowsocks.Controller
             }
         }
 
+        public void SaveHotkeyConfig(HotkeyConfig newConfig)
+        {
+            _config.hotkey = newConfig;
+            SaveConfig(_config);
+            if (ConfigChanged != null)
+            {
+                ConfigChanged(this, new EventArgs());
+            }
+        }
+
         public void UpdateLatency(Server server, TimeSpan latency)
         {
             if (_config.availabilityStatistics)
@@ -565,6 +575,8 @@ namespace Shadowsocks.Controller
             File.WriteAllText(PACServer.PAC_FILE, abpContent, Encoding.UTF8);
         }
 
+        #region Memory Management
+
         private void StartReleasingMemory()
         {
             _ramThread = new Thread(new ThreadStart(ReleaseMemory));
@@ -581,6 +593,10 @@ namespace Shadowsocks.Controller
             }
         }
 
+        #endregion
+
+        #region Traffic Statistics
+
         private void StartTrafficStatistics(int queueMaxSize)
         {
             traffic = new QueueLast<TrafficPerSecond>();
@@ -615,5 +631,7 @@ namespace Shadowsocks.Controller
             }
         }
 
+        #endregion
+
     }
 }