Refine the doc of layers.py

Fix v2_API equation for img_pool and maxout format.

* Fix bug in MergeModel.cpp.

* Add a c-api inferface to initilize the thread environment of Paddle and add a GPU example.

* Add some note for paddle_init_thread and move the inplementation of paddle_error_string into a .cpp file.

* Add some comments.

* init decoder_trainer

* can run

* fix lod

* add sharelod to cross_entropy_grad_op

* add avg_cost to fetch list

* modify learning rate

* can run

* optimie code

* add early exit

* fix print

* revert test_understand_sentiment_conv.py

* add act to fc

add print_operators_doc in travis ci

message cxx compiler version

* fix gpu memory allocation policy

* refine codes

* fix code style

* follow comments

add script to check the cpu env

add softsign into doc.

add graph in IntelOptimizedReadme

Install dmidecode in product docker image

* Add HasCUDNN to detect if CUDNN is installed or not

* Fix CI

add MKLDNN LRN

Compile cblas library as static

Make ConvTransProjection support for dilation

fix typo and path issue in build from source doc

Enhance AvgPooling to support both include_mode and exclude_mode

* write versino.py

* add version py

* clean init py

* add istaged, major and etc... fields

* update

* update

* update

Change the type of conv2d in Python API.

Add LRN efficient GPU implement

Add half precision float16 data type

* init nmt

* encoder ready

* only generation implementation

waiting for dynamic rnn ready to train

* init python

* remove decoder temporary

* clean

* clean