* 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

* add inference api doc. test=develop

* fix no cvm, when accessor is DownpourSparseValueAccessor, set no_cvm=True
* test=develop

test=develop

This reverts commit 23baf865.

* add dynamic plugin support.
test=develop

* change emb eltwise layernorm to math function
test=develop

* add emb eltwise layernorm
test=develop

* can run dynamic shape ernie
test=develop

* fix ci
test=develop

* add ut for trt ernie dynamic

test=develop

* refine dynamic shape c++ interface.
test=develop

* fix comments
test=develop

* fix comments
test=develop

* get pslib version
* test=develop

* support feed_python_builtin, test=develop

* add test, test=develop

* support CompiledProgram, test=develop

* support fluid.data, test=develop

* fix ci problems, test=develop

* follow comments, test=develop

* add clear_one_table
* test=develop

* fix bug when grad_op's output not be used in compute kernel in dygraph mode, test=develop

* fix test_data_norm_op.py, test=develop

* polish code style, test=develop

* fix error of data_norm's infershape, test=develop

* polish comment, test=develop

1. Add Decorator 'dygraph_to_static_program'
2. Add corresponding ProgramTranslator.get_program
3. Add ProgramTranslator.save_inference_model
4. Modified some warning information of dy2stat
5. Change program cache to contain startup_program because for users who gets program to run, they may like to initialize startup program

* add unittest test=develop

* add function cache test=develop

* add maskauc in paddlebox; test=develop

* Add parameter(learning_rate) in NoamDecay test=develop

This PR does exact the thing as the title. The reason is that we plan to develop 4 decorators

"dygraph_to_static_code"
"dygraph_to_static_program"
"dygraph_to_static_func"
"dygraph_to_static_output"

 The 4 decorators will emphasize different part when translating dygraph to static graph. Decorator name "dygraph_to_static_graph" is too big for the function it implements.

As the title, we add decorator "dygraph_to_static_code", and add related "get_code", "get_func", "get_output" for ProgramTranslator. Next step will be adding "dygraph_to_static_program"

* Polish error Info in while_loop test=develop