* fix-apis-develop

* fix-one-error

* remove Fake and fix layers_cn.rst

* fix-apis-develop

* fix-one-error

Add the description and example of shape tensor supporting int32

fix-contents_cn

* add dataset

* add back dataset and data feeder

* fix Layer and Pool2D api, test=develop

* update label_smooth_cn.rst, test=develop

* 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.

test=document_fix

* fix Layer and Pool2D api, test=develop

* update label_smooth_cn.rst, test=develop

* 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 save_load_variables.rst (#1520)

* update 1_6 release

* fix readme
test=document_preview

* add new tree index

* update 1_6 release

* fix readme
test=document_preview

* add new tree index

* add new seq2seq api_cn, test=document_preview

* add seq2seq api_cn, test=document_preview

* add seq2seq api_cn, test=document_preview

modify fluid.layers.data to fluid.data and Synchronize Chinese doc and English doc

Fix fluid.layers.data of example code, Synchronize Chinese and English DOC of API:layers.sum.

* Refine the Chinese documentation of DynamicRNN.
test=develop
test=document_preview

* Refine the memory interface of DynamicRNN.
test=develop
test=document_preview

* Refine update_memory and output of DynamicRNN.
test=develop
test=document_preview

* Update the format of note and fix a error in example.
test=document_preview

* Add name and correct some examples.

* Refine the documentation according to the review comments.

* Add function list and the doc of function __call__.

* Add optional for x in step_input.
test=develop

* Update sub-titles.

* Change fluid.layers.data in examples to fluid.data.

* Add examples for step and static input.
test=develop

* Refine some sentences.
test=develop

* Add description of shape and data type for input and output variables.
test=develop

* fix apis, test=document_preview

* fix apis, test=document_preview

* fix apis, test=document_preview

* fix apis, test=document_preview

test=develop

* fix sequence_enumerate cn doc

* only surpport LoDTensor

* add input output shape

* test=document_fix

* fix space_to_depth cn doc

* change name's text

* add input output shape

* add code example

* test=document_fix

* revision

* change name's text

* add input output shape

* test=document_fix

* update piecewise decay, test=develop

* update, test=develop

* update, test=document_fix

* update, test=document_fix

* update, test=document_fix

* update, test=document_fix

* update, test=document_fix

* update, test=document_fix

* update exponential decay, test=develop

* update,test=develop

* update, test=develop

* update, test=develop

* update, test=develop

* update, test=document_fix

* update, test=document_fix

* set inverse time decay file to original, test=document_fix

* set piecewise decay to original, test=document_fix

* update, test=document_fix

* update, test=document_fix

* update, test=document_fix

* update, test=document_fix

* update, test=document_fix

* update, test=document_fix

* update inverseTimeDecay, test=develop

* update, test=document_fix

* update inverse, test=document_fix

* update, test=document_fix

* update, test=document_fix

* update, test=document_fix

* update, test=document_fix