Support Socks5 proxy server mode

[certaintls]

Add a server socks5 proxy mode. The client side keeps using the transparent TCP mode.

Usage Example:

• Server side command

./shapeshifter-dispatcher -mode dynamic -server -state state -transports shadow -bindaddr shadow-123.123.123.123:2222 -optionsFile ConfigFiles/shadowServer.json -logLevel DEBUG -enableLogging

Please note, make sure the IP address 123.123.123.123 is public avaiable

• Client side command (same as TCP transparent mode)

./shapeshifter-dispatcher -transparent -client -state state -transports shadow -proxylistenaddr 127.0.0.1:1443 -optionsFile ConfigFiles/shadowClient.json -logLevel DEBUG -enableLogging

both shadowServer.json and shadowClient.json files are copied from this repo. Except using the real IP address of the server in ConfigFiles/shadowClient.json

Implementation status

• The organization of the code change isn't optimized, the priority is to show the proof of concept
• Please see more discussion at the parent issue Decide if this project should be the one to help PT get off the island #43
• The branch is based on Add a GitHub action to automate testing #42