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

Fix shadowsocks/shadowsocks-windows/#2458

* Fix shadowsocks/shadowsocks-windows/#2458

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

Support Windows 10 1903 Light Theme

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

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.

Add new hints and fixed some old interaction bugs

Support Windows 10 1903 Light Theme (Menu icon color)

Plugin arguments tooltip

Add check box to toggle plugin argument input

Improve the code readability useProxy test condition

Mentioned in PR #2219

Auto register hotkeys

* Update LogForm.cs
* Update ja.txt
* Update zh_CN.txt
* Update zh_TW.txt
* Update the control name

- Naming
- Cleanup
- Move logic to controller

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

* Translation
* Environment Variables support

* Add tooltips
* Translations

Move PerPixelAlphaForm's code into QRCodeSplashForm to avoid 2 derived class of Form in same file.

Before: QRCodeSplashForm -> PerPixelAlphaForm -> Form
After: QRCodeSplashForm -> Form

Because the splash is already on the target display, the target rect doesn't need to calculate with the screen position.

"Allow Clients from LAN" --> "Allow other Devices to connect"

- update mbedtls to 2.7.0, use new md5 api
- update libsodium to 1.0.16
- static link to openssl 1.1.0g, check libsscrypto repo for detail