merge PaddlePaddle/Paddle

Auto compare cpu and gpu function.

Add Pythonlib and PythonIntep FAQ

Replace m4 template by Dockerfile ARGs

Support rectangle input for CNN

Benchmark including PaddlePaddle, TensorFlow and Caffe.

fix bug when run test_layerHelpers multiple times

Add .dockerignore as an alias of .gitignore

Re-define the way we build Docker images

Demo: Generative Adverserial Nets

Fix --job=test

When the define_py_data_sources2 has both train_list and test_list,
for job=test, the trainer will create both dataProvider_ and testDataProvider_.
But dataProvider_ is not used. This causes SIGSEGV at finishAsync() because asyncLoader_ is not created.

Change-Id: If579f715f80a70ebc795094792c3436bfa0f5746

refine build_docker_image.rst