Always sip002

- Compared to 2c15276: changed socketsHttpHandler to HttpClientHandler due to legacy .NET Framework
- Use System.Net.Http.HttpClient for GeositeUpdater
- New update check mechanism: first download checksum and compare, only download GeoSite DB on different checksum
- Verifiy downloaded GeoSite DB by comparing sha256sum before committing the change

- Removed some legacy compatibility code from Program.cs as we are not using .NET Framework.
- Changed CurrentDirectory detection method so that Self-Contained .exe can have its configuration files in the same directory as the .exe instead of in the temporary folder.

- Use System.Net.Http.HttpClient for GeositeUpdater
- New update check mechanism: first download checksum and compare, only download GeoSite DB on different checksum
- Verifiy downloaded GeoSite DB by comparing sha256sum before committing the change

# Conflicts:
#	appveyor.yml
#	shadowsocks-csharp/Controller/Service/TCPRelay.cs
#	shadowsocks-csharp/Program.cs
#	shadowsocks-csharp/Properties/Resources.Designer.cs
#	shadowsocks-csharp/View/MenuViewController.cs
#	shadowsocks-csharp/packages.config
#	shadowsocks-csharp/shadowsocks-csharp.csproj

in case gfwlist no longer update

drop sysproxy.exe in net-core version

New option for ss:// URL association

Fixes https://github.com/shadowsocks/shadowsocks-windows/issues/2857

also with some i18n update

target set to net core 3.1
managed cryptography implementation, drop x86 only
few modify to make new target working