Move Fluid C++ code from /paddle to /paddle/fluid

move paddle/pybind/pybind.h to paddle/fluid/pybind/pybind.h, and cancel the test_parallel_op temporary

* Added an elementary test case for CSP

* removed input

* Rename test file to avoid running in CI

* Fix YAPF error

* Remove one line function handler

* Add unit-test and example

* Fix type error

* Fix unit test cases

* Fix init error for cudaplace

* Change unit-test options

* initial commit

* fix bug

* end of file fix

* address comments

Rewrite mixed_vector.h

Remove 'numel' checker in compare op

* initial commit

* minor fix

* remove redundency

* address comments

Delete "API" section from "Documentation"

create optimize block in pserver program

Fix the bias of fc when num_flatten_dims is not 1 in fluid layers

Add python wrapper for layer normalization.

* Save the inference model in Python example of recommender_system.

* Add infer() in Python unittest recommender_system.

* Add C++ inference unittest of recommender_system.

Simplify the cmake of inference

refine error msg and add unit tests for cpp reader

Optimize return all optimize and related ops