Release/2.5.7

no repeat random number generator by GangZhuo

The stock code use class Random to generate IV, the Random is pseudo random number generator. The IV maybe repeat, this will cause shadowsocks-libev closed the sockets with the error message 'invalid password or cipher'. Reference https://github.com/shadowsocks/shadowsocks-libev/issues/389

Solution is use class RNGCryptoServiceProvider to generate IV, of course it's lower performance, but a little bit.

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

Fix a tiny bug

Sometimes the users may hit enter key by mistake, and the form will
close without saving entries.

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

Add more clear log for exceptions occured in ICMP tests

# Conflicts:
#	shadowsocks-csharp/Controller/Service/AvailabilityStatistics.cs

# Conflicts:
#	shadowsocks-csharp/Controller/Service/AvailabilityStatistics.cs
#	shadowsocks-csharp/Controller/Strategy/StatisticsStrategy.cs
#	shadowsocks-csharp/View/LogForm.Designer.cs
#	shadowsocks-csharp/View/MenuViewController.cs

Note: This is a dirty hack.

2. store window's size & position in config file.
3. fix: scroll bar sometimes disappear while sizing the window.

1. WrapTextTrigger -> wrapTextTrigger
2. WrapTextTriggerLock -> wrapTextTriggerLock
3. TopMostTrigger -> topMostTrigger
4. TopMostTriggerLock -> topMostTriggerLock
5. ShowToolbarTrigger -> toolbarTrigger

1. add menu items for `clear logs`, `change fonts`, `wrap text` and `top most` functions.
2. hide toolbar default. but you can trigger it out by menu.

improved `log viewer` windows

1. add `clean log` feature
2. add `change font` feature
3. add `wrap text` feature
4. add `top most` feature

2 fixes, 1 feature, 1 code beautify