Support headless startup, x11vnc, noVNC and process control

[ChisBread]

1. Headless Startup: xvfb dummy X server (deprecated but works)
2. VNC: x11vnc server; noVNC for web user
3. Process Control: http://supervisord.org/
4. WindowManager: http://fluxbox.org/
5. GUI automation: xdotool
6. wechat-monitor: kill error windows, hide decorative windows
   These features only take effect when VNC_SERVER=1

[CLAassistant]

All committers have signed the CLA.

[huan]

Hi @ChisBread !

Thanks for your improvement; it's a lot of work for the system.

Before we can continue to review it, could you please file an issue and explain in detail how the whole PR system works?

Because without some details, I can not understand the details of each file, and I can not have full confidence to merge it.

Also, it would be great if you could invite 1-2 developers who are familiar with this system to give this PR an approvement to make sure everything is good to go!

Appreciate it, and have a great day!