Unify the guide content structure.

* fix typo in doc

* add faq for lod_tensor

* format the lod_tensor.rst

* fixed one error of api_cn

* fixed some errors of api_cn

* fixed some errors of api_cn

* fixed two errors.

* fixed two errors

* fixed one error.

* fixed one error

* fixed one error.

* fixed two errors.

* fixed one error.

* fixed two errors

* fixed two links

* synchronize api_cn with the api_en of develop.

* updated develop/api_cn

* update the api_cn of develop

* update api_cn of develop

* fixed some errors

* Delete .DS_Store

* Delete .DS_Store

* Delete .DS_Store

* Delete .DS_Store

* Delete .DS_Store

* fixed some wrong links

* fixed two links

* fixed two links and some error.

* fixed some errors.

* fixed two links

* http://newicafe.baidu.com/issue/DLTP-1771/show?from=page

* http://newicafe.baidu.com/issue/DLTP-1647/show?from=page

* http://newicafe.baidu.com/issue/DLTP-1529/show?from=page

* Update natural_exp_decay_cn.rst

* Update Reader_cn.rst

* http://newicafe.baidu.com/issue/DLTP-1907/show?from=page of develop

修改了DyGraph.md文件中加载图片的错误路径，使其与PaddleBook保持统一

* fixed one error of api_cn

* fixed some errors of api_cn

* fixed some errors of api_cn

* fixed two errors.

* fixed two errors

* fixed one error.

* fixed one error

* fixed one error.

* fixed two errors.

* fixed one error.

* fixed two errors

* fixed two links

* Update cluster_quick_start.rst

test=document_preview

test=document_preview

test=document_preview

test=document_preview

remove command argument train.py from the document, which is added by mistake.

* Update fleet_api_howto_cn.rst

* Update fleet_api_howto_cn.rst

* Update fleet_api_howto_cn.rst

* documents will be ready afterwards

not ready now

* Update index_en.rst

* Update index_cn.rst

* Update index_en.rst

* Update index_cn.rst

* Update index_en.rst

* fleet api

* fleet api

* fleet api

* improve the doc of metrics introduction

* tweak the doc of metrics introduction

* Modify errors in VisualDL usage manual
Including:
	line break errors;
	punctuation errors;
	Add explanation for each pictures.

* Modify errors in VisualDL usage manual
Both Chinese and English Documents are modified.
Including :
	line break errors.
	spell errors

* Modify the line break error in visualdl_usage_en
The Line break errors in visualdl_usage_en will make the demo program crash into errors.
I have fixed these errors.

* Modify the line break error in visualdl_usage_en.md
The errors have been fixed.

* Modify errors in VisualDL usage manual
Including:
	line break errors;
	punctuation errors;
	Add explanation for each pictures.

* Modify errors in VisualDL usage manual
Both Chinese and English Documents are modified.
Including :
	line break errors.
	spell errors

* update dygraph user guide to fit new api

* refine doc

* remove pylayer support doc

* refine words

* refine sample code

* Add usage manual for VisualDL
The usage manual will be helpful for beginners to make use of VisualDL.

Components of VisualDL are introduced in details, including:
	* Definition of Functions
	* Parameters explanation
	* Demo program for each component

* add_index

* modify write_docs_cn, write_docs_en, include specifications about python 2.7.15 and creating  virtual env with conda

* gitignore update

* revert .gitignore;  update write_docs

* icafe DLTP-1328, stress  exe.close()

* DLTP-1383 不可迭代更正

* DLTP-1404 修复动态图文档中每段代码的格式和大小都不一样

* DLTP-1390 Pyreader中文显示格式问题

* DLTP-1393 无效链接

* DLTP-1421 paddle.fluid.layers.reduce_max中文翻译有问题

* DyGraph 调整标签结构

* Polish executor doc

* fix typo

* Update native_infer.md

* Update use_py_reader_en.rst

* Update use_py_reader_en.rst

* Update use_py_reader_en.rst

* Update doc/fluid/user_guides/howto/prepare_data/use_py_reader_en.rst
Co-Authored-By: Nacosta123 <42226556+acosta123@users.noreply.github.com>

* Update use_py_reader_en.rst

* hotfix deadlink (#811)

* Update native_infer_en.md (#787)

* Update install_Windows_en.md (#790)

* Update install_Windows_en.md

* Update install_Windows_en.md

* Update cluster_howto_en.rst (#791)

* Update cluster_howto_en.rst

* Update cluster_howto_en.rst

* Update doc/fluid/user_guides/howto/training/cluster_howto_en.rst
Co-Authored-By: Nacosta123 <42226556+acosta123@users.noreply.github.com>

* Update doc/fluid/user_guides/howto/training/cluster_howto_en.rst
Co-Authored-By: Nacosta123 <42226556+acosta123@users.noreply.github.com>

* Update cluster_howto_en.rst

* Update index_cn.rst (#813)

* Update cluster_howto_en.rst

* Update cluster_howto_en.rst

* Update doc/fluid/user_guides/howto/training/cluster_howto_en.rst
Co-Authored-By: Nacosta123 <42226556+acosta123@users.noreply.github.com>

* Update doc/fluid/user_guides/howto/training/cluster_howto_en.rst
Co-Authored-By: Nacosta123 <42226556+acosta123@users.noreply.github.com>

* Update cluster_howto_en.rst