* update ptb to support remove build once; test=develop

* update orc; test=develop

* polish code, test=develop
Co-authored-by: Nzhongpu <2013000149@qq.com>

* fix mnist multi gpu save error; test=develop

* fix inference error; test=develop

* only run inference on rankid == 0; test=develop

* fix se_resnet model for Optimizer and Linear upgrade, test=develop

* polish code style for se_resnet, test=develop

test=develop

* update build_once for cycle_gan
test=develop

* add input_channel arg
 for cycle_gan
test=develop

test=develop

test=develop

* modify senta dygraph

* modify details

* update ptb model to use auto generated op functions, test=develop

* refine model code, test=develop

* refine model code, test=develop

* update ptb model, test=develop

test=develop

test=develop

* update ptb model to use auto generated op functions, test=develop

* refine model code, test=develop

* refine model code, test=develop

* add gru and bigru net

* add gru and bigru

* add gru and bigru

* Use new save/load api and change fluid.layers.data to fluid.data (#3547)

* Use new save/load api and change fluid.layers.data to fluid.data

* add check for paddle version

* Use new save/load api in ptb_lm (#3546)

* Use new save/load api in ptb_lm

* add check for paddle version

* unify reader to dataloader (#3488)

unify reader to dataloader

* Use new save/load api and change fluid.layers.data to fluid.data (#3547)

* Use new save/load api and change fluid.layers.data to fluid.data

* add check for paddle version

* Add beam search for dygraph Transformer.
Re-organize dygraph Transformer.

* Add custumed data support for dygraph Transformer.

* Add validation in dygraph Transformer.

* Update notes for multi-gpu for dygraph Transformer.

* user new save load in all dygraph modell; test=develop

* change load_dict to set_dict; test=develop

* using new load api

* merge

* add dygraph user guide in models/dygraph

* remove useless files

* fix model save

* fix doc

* update gan model

* update gan model time display

* update gan script

* update gan script

* using new load api

* fix transformer crashed when dropout seed get None

* fix ptb reader and remove useless language model; test=develop

* add ptb reader; test=develop

* using new load api

* test=develop, add license

add copyright for cycle_gan and se_resnext

* fix ptb author bug; test=develop

* fix ptb author bug; test=develop

fix ceroot path bug

* Update mnist_dygraph.py

fix bug

* add muti card support for se_resnext

* add some description to readme.md

* add ce for cyclegan

* fix code style

* add ce for ptb_lm

* Update mnist_dygraph.py

fix bug

* add ce to se_resnext

* delete useless comments and fix unique_name bugs

* add sentiment ce

* delete some comment

* fix code style

* Update mnist_dygraph.py

fix bug

* add muti card support for se_resnext

* add some description to readme.md

Update mnist_dygraph.py
fix bug
* add ce to se_resnext
* delete useless comments and fix unique_name bugs

* fix typo

* fix reademe

* fix init_path for test

* add se_resnext for dygraph

* add ce for dygraph mnist

* add ce for dygraph mnist

* del mnist_dygraph.py

* change mnist_dygraph to train

* fix print style

* add resnet

* fix ce bug

* fix ce decsription

* add ce for dygraph mnist

* add ce for dygraph mnist

* del mnist_dygraph.py

* change mnist_dygraph to train

* fix print style

* add multi process reader

* use distributed_batch_reader

load_persistables function returns a tuple which include parameters and optimizer