Translate statistics config

change default method to chacha20-ietf-poly1305

Use id instead of calculating server.Identifier()

BugFix #2657 win10 1903 黑色主题下， trayIcon 会消失的问题；

https://github.com/shadowsocks/shadowsocks-windows/issues/2657

Support Windows 10 1903 Light Theme

But Fix Support Windows 10 1903 Dark Theme

Format the proxy host name used in GfwListUpdater

Init JS variable in more reliable and quick way, reduce redundant code

Rewrite the Appveyor build pipeline

- Backup the original appveyor.yml as appveyor.yml.obsolete
- Fetch an official appveyor sample file as reference
- Create a test scope appveyor pipeline

- Redirect the nuget \3rd folder to ..\packages folder as default by
  remove the nuget.config file
- Update csproj file: remove unnecessary scripts for old nuget
  packages on old .Net framework
- Upgrade nuget packages to .Net framework 4.7.2 as the target framework
- Downgrade Fody to 4.2.1. The 5.0.0+ requires MSBuild 16 and above

Microsoft Docs is misleading, as always. dotnet/samples#1644

Directly create a WebProxy with IPAddress.IPv6Loopback.ToString() throws UriFormatException. Format the proxy host name to satisfy WebProxy.

(cherry picked from commit 084b6fe72c)

FIX: some crash about thread-safe in statistics

[fixes #2542] Fix accidental index invalidation

Fixed an invalid index that was unexpectedly caused when the configuration was abandoned, resulting in an list box index exception.

Refine PAC server

- Uncompress the text file for better version control
- Touch the PAC files in first place

- Split the file operations to new PACDaemon
- More precise matching logic for handling PAC content http request

Modify PAC request behavior

Update the PAC file using the proxy channel only when proxy mode is enabled.

#2480 #1004

Fix shadowsocks/shadowsocks-windows/#2458

* Fix shadowsocks/shadowsocks-windows/#2458

* Servers List Box position adjustment is consistent with the v4.1.6 version

Add Experimental.md

issue_template: ask users to delete the instruction text

Support Windows 10 1903 Light Theme

留着每次读起来都很蛋疼，让用户看完就删了吧。