test=develop

* add attr axis infershape. test=develop

* add CUDA kernel. test=develop

* fix unittest. test=develop

* fix unittest for soft_label. test=develop

* fix fp16 unittest. test=develop

* remove comment code. test=develop

* refine test for axis. test=develop

* add python api. test=develop

* fix doc. test=develop

* fix fp16 unittest. test=develop

* fix ngraph test. test=develop

* fix ENFORCE for test_imperative_transformer. test=develop

* fit for ngraph test. test=develop

* fix after rebase develop. test=develop

* fix doc. test=develop

* fix API.spec. test=develop

* fix test_layers. test=develop

* fix format. test=develop

test=develop

test=develop

test=develop

test=develop

test=develop

test=develop

test=develop

* add ignore index

* update api.spec

* enhance softmax_with_cross_entropy

removed diagnostic

- Added Unit tests for Softmax MKLDNN Forward

Added fix for div by 0 to happen in cross_entropy backward

Conflicts:
	paddle/fluid/operators/CMakeLists.txt

- Cosmetic fixes to SoftMax MKLDNN fluid operator

Added misssing softmax fluid operator file

Disabled MKLDNN softmax operator by default

Fix to softmax op unittest merge

clang_formater fixes

clang_formatter fixes

- Name changing of softmax mkldnn operator to maintin consistency
  across codebase

- updated comment

fix to comment

There are mainly following fixes:

- take `DeviceContext` as the template parameter of math functors and OpKernel instead of `Place`
- remove `eigen_device` interface in base class  `DeviceContext`
- remove `GetEigenDevice` interface in `ExecutionContext` and base class `DeviceContext`
- remove unused `platform::EigenDeviceConverter`
- rename `REGISTER_OP_GPU_KERNEL` to `REGISTER_OP_CUDA_KERNEL`
- rename `USE_GPU_ONLY_OP` to `USE_CUDA_ONLY_OP`

* add sparse support for sum op

* typo fix

* fix gpu build error

* fix unittest error

* typo fix

* infer var type and shape in op_test

* follow comments

* fix build error

* bypass some unittests depend on NetOp

* support sparse output for lookup table grad op

* refine codes

* fix gpu build error

* fix lookup table grad gpu kernel

* fix ci

* fix ci

* fix ci

* fix bug in lookup_table_grad op

* fix bug in test_word2vec

* register double kernel for some operators

* set is_sparse=True in test_word2vec

* fix lookup table grad op CUDA kernel bug

* disable test_modified_huber_loss_op temporarily

* disable test_lstm_unit_op temporarily

* Change dataType to data_type

Follow PEP8

* Change name_convention to fit PEP8