* update gradient comment in Variable API, test=develop

* add sample code for Variable's gradient api, test=develop

test=document_fix

* Add descending parameter for argsort doc.

* Refine doc

* Refine format

test=document_fix

update 1.6.0 inference_lib of Windows to 1.6.1

* fix dead links for models

* fix_dead_links

update x2paddle link

* update DetectionMAP reference

* Update DetectionMAP_cn.rst

* fix_content_cn (#1579)

fix-contents_cn

* fix-apis-develop

* fix-one-error

* remove Fake

* fix layers_cn.rst

* fix_content_cn (#1579)

fix-contents_cn

* fix-apis-develop

* fix-one-error

* update paddle version in DyGraph.md, test=develop

* update paddle version in DyGraph.md, test=develop

* update_release_note

* update comment

delete the cuda8.0 links in cn and en doc except trt related and add more info about how to use capi, test=develop (#1557) (#1560)

fix the cmake command. Remove snappy and snappystream.

fix inference lib package on windows

* Update save_load_variables.rst (#1520)

* update 1_6 release (#1522)

* New tree (#1525)

* update 1_6 release

* fix readme
test=document_preview

* add new tree index

* Add save load save_dygraph load_dygraph (#1519)

* add save load save_dygraph load_dygraph, test=develop

* add .idea in gitignore, test=develop

* minor fix, test=develop

* doc refines, test=develop

* doc refines, test=develop

* Update custom_op.md (#1528)

* refine_design_idea_doc, test=develop (#1533)

* Add basic concepts (#1530)

* add cn docs, test=develop

* refine docs, test=develop

* add program doc, test=develop

* fix links, test=develop

* fix links, test=develop

* fix links, test=develop

* fix links, test=develop

* Fluid -> Paddle, test=develop

* Fluid -> Paddle, test=develop

* minor fix, test=develop

* minor fix, test=develop

* add Categorical and MultivariateNormalDiag doc (#1517)

* fix typos and links, test=develop, test=document_preview (#1514)

* Update programming_guide.md, test=document_fix (#1534)

重新组织了"新手入门>编程指南"中文文档，去掉了部分基础概念的详细介绍，比如Tensor，program等，本文档中更加注重对paddle静态图使用方式的说明

* Add C-API inference document and provide demo in the doc (#1526)

* add C-API inference document and provide demo in the doc

* fix Layer、label_smooth and Pool2D api, test=develop (#1506)

* fix Layer and Pool2D api, test=develop

* update label_smooth_cn.rst, test=develop

* modified cn doc for attr(shape) supporting -1, test=develop (#1531)

* Add gather_tree_cn.rst (#1537)

* Polish cn doc fo gru_unit, lstm_unit and scaled_dot_product_attention.

* Add gather_tree_cn.rst and update the data type of assign/fill_constant_batch_size_like/gather_nd.

* Fix _cn_api_fluid_layers_gather_tree

* Update tensor_array_to_tensor and add mse_loss.

* Update index_cn.rst

* Add GetExpectedKernelType method override rule to op_notes (#1527)

* add GetExpectedKernelType func override tule to op_notes

* add examples url

* add exemples to whether override method

* polish description

* polish doc based review comments

* Update deploy_ctr_on_baidu_cloud_cn.rst  (#1518)

* Add picture for deploy_ctr_on_baidu_cloud_cn.rst

* Baidu yun K8S + Volcano CTR Training Document 1.0

* Add ctr_pserver_log.png for deploy_ctr_on_baidu_cloud_cn.rst

* Update deploy_ctr_on_baidu_cloud_cn.rst

* Update deploy_ctr_on_baidu_cloud_cn.rst

* Add pserver-log

* Update deploy_ctr_on_baidu_cloud_cn.rst

* chanage image of kubectl download version from 1.13.3 to  1.13.4

* Update deploy_ctr_on_baidu_cloud_cn.rst

* Update deploy_ctr_on_baidu_cloud_cn.rst

Update on Sept 18. 
remove description of helm, tiller, Go install.
replace new yaml provided by Jinghui Zhang

* add some images

* Update deploy_ctr_on_baidu_cloud_cn.rst

add model output manipulation part

* Update deploy_ctr_on_baidu_cloud_cn.rst

* update deploy ctr on baidu cloud cn.rst

* auto convert from md

* Update deploy_ctr_on_baidu_cloud_cn.rst

* replace the overview.png

* Update deploy_ctr_on_baidu_cloud_cn.rst

* Update deploy_ctr_on_baidu_cloud_cn.rst

* Delete train_on_baidu_cloud_en.rst

it is outdated and cannot match with Chinese Version for months.

* Delete train_on_baidu_cloud_cn.rst

Has been replaced by ELASTIC CTR

* Update deploy_ctr_on_baidu_cloud_cn.rst

* Update deploy_ctr_on_baidu_cloud_cn.rst

* Update deploy_ctr_on_baidu_cloud_cn.rst

* Update deploy_ctr_on_baidu_cloud_cn.rst

* [Paddle-Lite] add Paddle-Lite doc test=document_preview (#1545)

* change the version number of windows inference (#1549)

* Delete duplicate file api_tree

* fix inference api (#1546)

test=develop

* 1026 develop (#1551)

* add dataset

* add back dataset and data feeder

test=develop

* add C-API inference document and provide demo in the doc

* fix Layer and Pool2D api, test=develop

* update label_smooth_cn.rst, test=develop

test=document_fix

Cherry-pick #1534

* Update save_load_variables.rst (#1520)

* update 1_6 release

* fix readme
test=document_preview

* add new tree index