test=develop

* add overrider for virtual function; test=develop

* fix layer.h OutputName bug; test=develop

* add _get_all_register_op_kernels api test=develop

* refine usage of check_op_register_type test=develop

* add import in core test=develop

test=develop test=document_fix

* fix the compatiable problem between PY2 and PY3.

* add ut, test=develop

* add proxy, test=develop

* download dataset before test, test=develop

* add ernie-large test
test=develop

* add ernie large c++ inference test
test=develop

* support SelectedRows in dygraph, test=develop

* fix bug of _grad_ivar interface, test=develop

* add optest for support seletedrows, test=develop

* fix bug for gradient_accumulator in GPU mode, test=develop

* fix error when Selectedrows addto LodTensor in sorted_gradient mdoe in dygraph, test=develop

* refine and simplify gradient accumulator code, test=develop

* add optest, test=develop

* add optest and simplify code, test=develop

* fix bug for test_imperative_selected_rows, test=develop

* add optest for Coverage, test=develop

* fix gradient interface and simplify code, test=develop

* update api for gradient, test=develop

* fix ShareDim's bug in DygraphExecutionContext class, test=develop

* add optest, test=develop

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

* add jeston compile support
test=develop

* refine the cmake
test=develop

* fix adam sample code bug test=document_fix

* fix sample code bug in scale test=document_fix

test=develop

This reverts commit 007c9975.

* fix default grad op maker ci bug, test=develop, test=document_fix

* remove some ops from paddle/fluid/op_use_default_grad_op_maker.spec, test=develop, test=document_fix

This reverts commit c93c9e5b.
test=develop

Add warning message when initialize GLOG failed

* fix -Wno-error=sign-compare warning in gcc8

test=develop

* fix warning in distributed codes

test=develop

* fix transpose conv,test=develop

* fix comments
test=develop

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

There are PythonAPI tests in Op's unittest which don't need to inherit OpTest class.

* 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

* fix shape check in density_prior_box, test=develop

test=develop