test=develop

* refine the error message of tensor_array_read_write Op

1. Add data_layer_not_check because it is needed in dygraph_to_static where input can be variable size
2. Remove warnings in static analysis because python cannot do exact static analysis

* add attr support for fusion group and add support for fill_constant and scale Op

* add fleet pslib pull and push sparse op and push dense op
* test=develop

test=develop

test=develop

* Remove Read-Only Basic Type Variable in loop_vars

test=develop

* Put class support in loop for future thing

test=develop

* Modify based on reviewer's comment

test=develop

As nccl comm is not created by CUDADeviceContext, it should be destroyed by the creator as the best practice of RAII.

* refine output of profiler for child event 

* expand parameters, test=develop

* support resnet, test=develop

* fix resnet, test=develop

* support duplicable out, test=develop

* support ptb

* fix bugs, test=develop

* support null input, test=develop

* fix bugs, test=develop

* fix batchNorm is_test, test=develop

* refine code, test=develop

* follow comments, test=develop

* follow comments, test=develop

* follow comments, test=develop

* follow comments, test=develop

* Support Parameter type determination test=develop

* support math operator for variable, test=develop

* polish code, test=develop

* polish code, test=develop

* define alias in paddle dir and paddle.nn dir test=develop

* define alias in paddle.nn.functional dir test=develop

* define alias in paddle.tensor.__init__.py test=develop

* distinguish public/private vars, test=develop

* fix windows issues, test=develop

* Improve elementwise performance.

Elementwise performace is poor as walk into CommonGradBroadcastCUDA, add some new kernels for different data pattern.

* Add some cuda kernel to speedup common broadcast cases. test=develop

* Add more test cases and fix cuda kernel bug. test=develop

* Remove tests as cpu percision fails.test=develop

* Refine SplitDims, test=develop

* Change file mode, test=develop

* expose dygraph.grad api, test=develop, test=document_fix

* add more parameter in dygraph.grad API, test=develop

* add only_inputs=True parameter, test=develop

* follow comments, test=develop, test=document_fix

* fix typo, test=develop, test=document_fix