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。

When launch from test framework, the Application.StartupPath looks like "C:\PROGRAM FILES (X86)\MICROSOFT VISUAL STUDIO\2019\COMMUNITY\COMMON7\IDE\EXTENSIONS\TESTPLATFORM" which may not have write permission.

Support local IPv6 listener

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

Turn off per-monitor DPI awareness as it is not supported

Fixed bug of #2379 pullrequestreview-254461303
Redundant paintings when user move mouse on the icon, pixel by pixel.

Refactoring Config Form

Upgrade appveyor image to Visual Studio 2017

Move GetWindows10SystemThemeSetting() to Util.cs
WindowsThemeMode use enum
Status var windowsThemeMode rename to windowsThemeMode
Used `if else` to replace `switch case`
Delete legacy commint (Some code).
Increase contrast for icon.

Added Config Form hint text

Add new hints and fixed some old interaction bugs

Fix udp relay

fixed issue #2371

Fixed a bug with + in query

Support Windows 10 1903 Light Theme (Menu icon color)

Plugin section

Plugin arguments tooltip

When error code is SocketError.AccessDenied/10013(WSAEACCES), the port is reserved by system and you may not find the process name in `netstat`.
 https://github.com/shadowsocks/shadowsocks-windows/issues/1835#issuecomment-453528715

Add "Apply" button to Editor Servers form

Enhance context menu  for System proxy and it's mode.

add "basic access authentication" support for http proxy @rickryo