Support custom GFWListUrl defined in config file

Support local IPv6 listener

# Conflicts:
#	shadowsocks-csharp/Model/Configuration.cs

Add new hints and fixed some old interaction bugs

- Portable mode ON: executable file's folder
- Portable mode OFF: current user's temp folder

* Translation
* Environment Variables support

if user manually deleted the whole 'configs' field in gui-config.json.
Which won't crash the app but will lost all other configs.

Also, fix typo in ProxyForm

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

* Add HTTP proxy support in forward proxy

Signed-off-by: noisyfox <timemanager.rick@gmail.com>

* Typo

* Throw exception if forward proxy not supported.

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>

- Only use one instance of LogForm

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

- Move to seperate model

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

# Conflicts:
#	shadowsocks-csharp/Controller/Service/TCPRelay.cs
#	shadowsocks-csharp/Controller/ShadowsocksController.cs
#	shadowsocks-csharp/View/MenuViewController.cs

Note:
- Added a configuration entry, user should add this
  by hand or reset from scratch.

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

# Conflicts:
#	README.md
#	shadowsocks-csharp/Controller/Service/AvailabilityStatistics.cs
#	shadowsocks-csharp/Controller/Service/PACServer.cs
#	shadowsocks-csharp/Controller/Strategy/SimplyChooseByStatisticsStrategy.cs
#	shadowsocks-csharp/Data/cn.txt
#	shadowsocks-csharp/Model/Configuration.cs
#	shadowsocks-csharp/Model/LogViewerConfig.cs
#	shadowsocks-csharp/View/LogForm.Designer.cs
#	shadowsocks-csharp/View/LogForm.cs
#	shadowsocks-csharp/View/MenuViewController.cs

1. Add Logging.Info()
2. Console.WriteLine() -> Logging.Info()
3. Console.WriteLine() in exceptions -> Logging.LogUsefulException()

Import Json.Net since it's difficult for SimpleJson to deal with nested type.

Strategy: Simply Choose By Statistics