Add a python interface for Gelu.
    Add documentation for fluid.layers.gelu.

* dygraph mode support linear lr warm up; test=develop

* add unitest for linear warmup; test=develop

* add input type check; test=develop

* fix type check assert error; test=develop

* change type error; test=develop

* test=develop, fix docker with paddle nccl problem

* don't expose numerous Tensor.set(), test=develop

* fix condition, test=develop

* fix float16 bug, test=develop

* feed should be Tensor or np.array, not Variable or number, test=develop

* use forcecast to copy numpy slice to new array, test=develop

* remove float16-uint16 hacking, test=develop

* add variable method to varbase and refactor to_variable to support return varbase

* support kwargs in varbase constructor

* add VarBase constructor to support default python args

* refine varbase initial method

* reset branch

* fix ut for change VarBase error info to PaddleEnforce

* cherry is parameter change before

* overload isinstance to replace too many change of is_variable

* rm useless files

* rm useless code merged by git

* test=develop, fix some ut failed error

* test=develop, fix test_graph_wrapper

* add some tests, test=develop

* refine __getitem__, test=develop

* add tests, test=develop

* fix err_msg, test=develop

* fix fill_constant_batch_size_like_op precious problem  test=develop

* set dim[0] to -1 if dim[0] < 0 and remove assertion to runtime, test=develop

* modify ENFORCE message, test=develop

* add validation for x.shape[0] > 0, test=develop

* add ut, test=develop

* fix adam sample code bug test=document_fix

* fix sample code bug in scale test=document_fix

This reverts commit 007c9975.

* refactor AUC OP and add its CUDA Kernel
* the layout of global auc doesn't change

* fix the device supported of the op unique and unique_with_counts.
test=develop
test=document_fix

* Fix the precision of test in the op of unique and unique_with_counts.
test=develop
test=document_fix

Add English doc for cond

* Commit before merging develop

test=develop

* Backup after working with Huihuang logs

* Commit before deleting Huihuang debug loggings

* Commit before debug

test=develop

* Fix bug commit

test=develop

* Backup of fixing bugs

test=develop

* Clean up code

test=develop

* Fix a bug in sum_op

test=develop

* Add ascending for argsort

* Refine api doc description.

* Refine descending description

* Add int32 logic to speedup when data is small size.

* Remove int32 opt as not support in python

* add Adam beta1/beta2 support Variable. test=develop

* batch_norm momentum support variable. test=develop

* fix format. test=develop

* add batch_norm momentum variable example. test=develop

* move MomentumTensor to training branch. test=develop

* split example. test=develop

* fix doc. test=develop

* fix PADDLE_ENFORCE ci. test=develop

* fix format. test=develop

* support data_norm_op run in CUDA
* add two parameters sync_stats & summary_decay_rate
* add UT

* add the framework support for distfc and ut, test=develop
* fix the implementation of shard_index_op, test=develop

* fix the fill_constant op precious problem test=develop

pass the argument `allow_out_of_range` of one_hot op to c++ back end.

* add input type and input data type check for Print_op test=develop

* add control flow API: case. test=develop

* delete 'raise TypeError' in _error_message() and return a string. test=develop

* polish API document. test=develop

* fix auc drop first commit test=develop

* update datanorm op

* update datanorm with enforce test=develop

* update test=develop

* update format test=develop

* update format

* update format test=develop

* add unit test test=develop

* update unit test test=develop

* update format test=develop

* update format test=develop

* update API description test=develop

* update API description test=develop

* update format test=develop

* fix codes as comments test=develop

* fix description as comments test=develop

* fix description as comments test=develop

* update codes.. test=develop

* modified error message for conv and conv_transpose, test=develop

* modified doc of conv and conv_transpose op, test=develop

* modified the expression for error message, test=develop

* modified error message for group_norm op, test=develop

* modified detail of Attr(data_format) or Attr(data_layout)

* add ValueError in API doc for maxout op, test=develop

* add API switch_case. test=develop

add Nest

* modify code according to reviews:
1.Attr(branch_index) support 'uint8' and 'int64' besides 'int32'.
2.remove useless code.
test=develop

* replace fluid.layers.data with fluid.data and polish API document. test=develop

* add input type and dtype check template, and update some APIs check

* refine check template, and update some APIs check in nn.py

* update some APIs check in loss.py

test=develop

* Split some APIs from nn.py to loss.py

test=develop

* fix test_detection unit-test

test=develop

* set the default value of alpha for prelu to 0.25, test=develop

* add the call to __syncthreads(), test=develop

* fix the implementation of cpu prelu, test=develop

* repair the implementation of element mode prelu, test=develop

* modify test_prelu_op.py, test=develop