* add distributed dir and doc

* remove start_processes & move DataParallel

* add get rank and world size

* add cn docs

* add index to distributed_cn

* add white list api

* add api white list

* add cn to api name

* polish details

* add rst suffix

* add py function

* add DataParallel cn doc

* polish details

* fix method declarative error

* polish format

* fix sample code error

* append to white list