fix chinese doc of gradient_clip 

fix regularizaiton documention to dispel puzzle of user

* sync recompute doc btw zh and en, test=document_preview

* test=preview

* remove FC, test=develop

* delete en_doc for fc, test=develop

* polish code style, test=develop

* change FC to Linear, 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

* add DpsgdOptimizer zh doc test=develop

* modify api_white_list test=develop

* add update way test=develop

* fix comma in parameters test=develop

* polish backward api doc test=develop, test=document_preview

* polish backward api doc test=develop, test=document_preview

* polish doc of optimizer test=develop, test=document_preview

* polish doc of optimizer test=develop, test=document_preview

* polish doc of optimizer test=develop, test=document_preview

* polish code of no_grad_set test=develop

* update adam_op, scale_op, batch_norm_op doc. test=develop

* fix batch_norm example indent. test=develop

* polish model average zh doc api

* polish details

* polish based review commment

* fix indent

This reverts commit a29dcbec.

* Fix problems of chinese docs

* Revise chinese docs

* Add more fixes

* Add data type comments for some inputs

* fix the chinese doc for paddle test=develop
paddle.fluid.layers.create_global_var
paddle.fluid.layers.create_parameter
paddle.fluid.optimizer.FtrlOptimizer
paddle.fluid.optimizer.LarsMomentumOptimizer
paddle.fluid.optimizer.MomentumOptimizer
paddle.fluid.optimizer.RMSPropOptimizer
paddle.fluid.optimizer.SGDOptimizer

* polish decayed adagrad opt zh api doc

* change the note position

* delete return and return type

* polish details

* use whole optimizer name

* polish adamax optimizer zh doc

* polish details

* use whole optimizer name

* polish adam optimizer zh api doc

* polish details

* polish adagrad optimizer api zh doc

* polish details

* polish seven minimize api zh doc

* polish details

* enrich grad_clip param comment

* add RecomputeOptimizer_cn.rst

* modify RecomputeOptimizer_cn.rst
test=develop

* modify RecomputeOptimizer_cn.rst
test=document_preview

* modify RecomputeOptimizer_cn.rst, test=document_fix

* modify optimizer_cn.rst. test=document_fix

* modify optimizer_cn.rst. test=document_fix

* modify RecomputeOptimizer_cn.rst, test=document_fix

* add LookaheadOptimizer_cn.rst (#1360)

* add LookaheadOptimizer_cn.rst
test=document_preview

* modify LookaheadOptimizer_cn.rst, test=document_fix

* modify LookaheadOptimizer_cn.rst, test=document_fix

* modify LookaheadOptimizer_cn.rst, test=document_fix

* modify RecomputeOptimizer_cn.rst, test=document_fix

* delete unused files

* add LookaheadOptimizer_cn.rst
test=document_preview

* modify LookaheadOptimizer_cn.rst, test=document_fix

* modify LookaheadOptimizer_cn.rst, test=document_fix

* modify LookaheadOptimizer_cn.rst, test=document_fix

* add AdadeltaOptimizer cn doc, test=develop

* refine adadelta optimizer doc again, test=develop

* 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

* 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