Rewrite root README.md file

[wangkuiyi]

List componenets:

1. paddlectrl (Go)
2. paddlecloud (Python)
3. paddlefs (PFS, Go)
4. EDL controller (Go)

Add a figure to explain how these components interact with each other. #593

[typhoonzero]

I suppose the root README.md have the following structure:

• Introduction
  • What this repo does, what it contains, what kind of ability can users get from this repo.
• Components
  • client: paddlectl
  • paddlecloud server
  • paddlefs
  • EDL
• User Manuals
  • link to the tutorial
  • command line reference
  • FAQs
• Build
  • link to build EDL
  • link to build EDL controller image
  • build paddlecloud-job docker image
  • build paddlectl
• Deploy
  • link to deploy paddlecloud
  • link to deploy EDL
  • link to deploy on minikube
• Contribute
  How to contribute code. link to code structure and design docs.

[Yancey1989]

Add items:

• Deploy
  • Link to deploy PaddleFS server
• User Manuals
  • link to the benchmark

[gongweibao]

Maybe we can add develop-guide like this

[typhoonzero]

Awesome, will update the PR.