* "fix decode bug"

* "follow commnet"

* "fix error"

* "fix hook bug"

* fix based comment

* fix copyright

* fix based on comment

* update cluster train v2 doc

* WIP cluster train doc

* update

* cluster train doc

* add TOC for en doc

* fix sphix build issue

* fix error links

* fix link errors

* fix image link

* polish cluster train docs

* update general distributed training document

* fix sphinx compile error

* fix doc image error