Use PHPDoc for Task & Transformer Reference

[njoubert-cleverage]

From #125

Description

Today, reference documentation is lacking a lot of information, and some might be quickly obsolete...

The goal of this PR is to put a maximum of documentation right into PHPDoc

• more visibility for people looking into code
• less risk of difference between the code & doc

I tried to use https://phpdoc.org/ to generate a static website to help peeking into content.

There's still on-going documentation work. Some customization has been added in the .phpdoc folder

Requirements

• Documentation updates
  • Reference : push more and more task / transformer reference into PHPDoc and remove the old .md file
  • Find some hosting solution
  • Cookbooks
  • Changelog
• Unit tests

Implementation notes

To build the doc, use make build/sf4 doc

Breaking changes

None