[Cherry-pick #1810] Update doc 'programming_guide.md', using new control flow APIs as example (#1815)

Update doc 'programming_guide.md', using new control flow APIs as example, see #1810 for details

* update cpu distribute practice

update fluid.layers.data to layers.data

* update install doc for 1.7.0, test=develop

* update table.md, test=develop

* fix cuda support, test=develop

update cpp inference lib link of windows

As the title

As the title

topk chinese doc code example fails as same input names

* remove FC, test=develop

* delete en_doc for fc, test=develop

* polish code style, test=develop

* change FC to Linear, test=develop

* update load api_cn, test=develop

* polish api comment, test=develop

* fix code bug, test=develop

* polish api comment, test=develop

Add the override function in the elementwise ops

* expose load_program_state and set_program_state api, test=develop

* polist api comment, test=develop

add clear_gradient、current_step_lr api and parameter_list parameter for optimizer in dygraph (#1694)

* add clear_gradient function and parameter_list parameter for optimizer, test=develop

* fix AdagradOptimizer_cn.rst, test=develop

* add sample code, test=develop

* polish sample code, test=develop

* polish description for clear_gradient, test=develop

* add current_step_lr api for optimizer, test=develop

* improve doc of module evaluation and CosineDecay API

* tweak doc of CosineDecay

* add load_op_library cn doc

* fix grammar

* fix op cn name,test=develop

add the doc of prepare_context

fix save_dygraph cn doc error and sample code error

* add DpsgdOptimizer zh doc test=develop

* modify api_white_list test=develop

* add update way test=develop

* fix comma in parameters test=develop

Add Chinese doc of required_version， corresponding to Eng version： https://www.paddlepaddle.org.cn/documentation/docs/en/api/fluid/require_version.html#require-version

As the title

* update index for cn & en doc
* remove duplicated items

add doc for erf into index