new document to upload in this PR

the previous doc talks about how to run CTR training on Baidu Cloud K8S Cluster.

the new doc are modified in following points.

1.Run CTR Training on Baidu Cloud K8S + Huawei Volcano
2.Auto Split CTR model into sparse ones and dense ones.
3.Cube auto fetch Sparse model, Serving auto fetch dense model.
4.provide paddle serving client to test the ctr prediction.

* 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

* fleet api

* fleet api

* fleet api

* 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

* 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

* save load implement optimize

* fix.

* recheck_structure&fix_typo

* fix_structure

* adjust_dist_structure

* fix_deadlink

* fix deadlink

* Update single_node.rst

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

* Update single_node.rst

* Add compiled_program.py

* polish doc

* follow comment

* modify user_guide_howto_training_1

* remove server after pserver

* add deploy ctr doc on baidu cloud
test=develop

* test=develop

* test=develop

* test=develop

* improve save_load_variables

* Update save_load_variables.rst

* add launch mp distributed job

* fix comment

* update by comment

* test_while_training

* Textual Review

Textual Fix

* single_node

* Textual Fix

* review on webpage

* upload train_on_baidu_cloud_en

* First round review check

* review on webpage, fix minors

* upload save_load_variables_en

* Textual Review

* upload enhowto

* upload cluster quick start en

* review commit

* recover original multi_node.rst index

* fix index of cluster_howto

* fix index

* fix bugs

* 0123-routine-docbug-fix

* Update metrics.rst

* polish

* add_api_cn (#437)

* add gpu benchmark page (#436)

* add gpu benchmark

* fix comments

* add chinese link in gen_doc.py (#439)

* modified gen_doc.py

* Update gen_doc.py

* update gen_doc.py

* Update mobile doc (#440)

* update_en_structure

* update_Paddle_commitid

* delete_DS

* update_mobile_doc

* Update book commit (#438)

* update_en_structure

* update_Paddle_commitid

* delete_DS

* update_book_commit_id

* update_api_rst

* Adjust structure of advanced usage (#442)

* adjust_structure_of_advanced_usage

* Update paddle_gpu_benchmark.md

* adjust_toctree_hidden

* fix_api_guide

* Update index.rst

* fix deadlinkes (#443)

* add_toctree (#445)

* adjust_beginners_structure (#446)

* adjust_beginners_structure

* Update index.rst

* update install_doc for python3 (#418)

* update install_doc for python3

* update python3.5+ info,test=develop

* fix review, test=develop

* fix_pic (#447)

* delete en2zn link

* update lod_tensor

* 1207

 1.english api reference links removed
2. formatted

* update transpiler

* update profilse_cn

* Update docker-image instroduce, test=develop (#459)

* fix_bug (#460)

* [cp2dev]Add avx info 1.1 (#279) (#451)

* Add avx info 1.1 (#279)

* refine avx info representation

* refine avx info representation

* refine avx info representation

* updatetoavx

* fix_AVX

* update_en_api (#461)

* update api guides for cn (#462)

* Update commit_id of Paddle (#463)

* update_en_api

* update_again

* Fix bug (#465)

* update_en_api

* update_again

* bug_fix

* fix_2nd