* add .rst file of 4 control flow APIs

* add Note in docs of control flow. test=develop

* Add Chinese Doc for cond API

* add Chinese document of control flow API case and switch_case. test=develop

* polish TypeError according to reviews. test=develop

As the title

This reverts commit 6f6cc947.

* add recompute document

* fix-apis-develop

* fix-one-error

fix-contents_cn

* add filter to simplify optimizer api doc

* update related optimizer doc

* skip PipeReader in IO

* skip PipeReader in IO
test=develop

* fixed bugs about PipeReader

This reverts commit a29dcbec.

* polish seven minimize api zh doc

* polish details

* enrich grad_clip param comment

* skip PipeReader in IO

* skip PipeReader in IO
test=develop

* test=document_preview

* 0823 update FluidDoc,test=document_preview

* add two files

* ok

* ok

* ok

* add check_approval

* check approval

* check approval

* check approval

* check approval

* check approval

* check approval

* add check_approval

* add check_approval

* add check_approval

* add check_approval

* add check_approval

* change api

* change api

Create a special case for dygraph-node when running gen_doc.

1.add dygraph api doc
2.add dygraph node

* add flag files

* add flags file

* delete space

* split layers,test=develop

* split nn layers

* remove nn header, test=develop

* update en api doc

* update Paddle commitid

This reverts commit 76d8f574.

* update_commitid_Paddle_0428

* run gen_doc

* update_Paddle

* update_book

* update_to_1.4