* add fp16 mul op support

* small fix

* fix bug

* small fix

* fix PADDLE_WITH_CUDA compiling issue

* reorg code

* test for pybind

* treate as float16 as uint16_t in pybind

* bind np.float16 to paddle float16

* small fix

* clean code

* remove redundancy

* fix mul_op test

* address comments

* small fix

* add is_float16_supported func

* "exported scatter to python"

* Revert ""exported scatter to python""

This reverts commit 38745a62.

* "polish scatter and export to python"

enable WITH_FLUID option

Refine parallel_do_grad

Add a test to ensure profiler works on multi-gpu

Move back operator's event to RunImpl()

Fixed some outdated contents in Contribute Documentations

Feature/shuffle reader

Add product reduction for reduce op.

Enhance regularizer.py

Fix distributed train doc deadlink

Add api doc std

Merge branch develop

* "Refine nccl op"

* "refine code "

* "refine nccl code"

Merge branch 'develop' of https://github.com/PaddlePaddle/Paddle into feature/Enhance_regularizer_py

Enhance look_up_table op 

move fluid dist design to fluid folder

Adjust some contents and create a new folder src to store pictures.