- Put the 'ARG DEBIAN_FRONTEND=noninteractive' ahead of the first
  'apt-get install' invoke.
- Add comments to Dockerfiles to explain why we're adding Bazel
  installation.
Signed-off-by: NLi Peng <lipeng@unisound.com>

Also add DEBIAN_FRONTEND=noninteractive to suppress the debconf
messages.

some tiny fix

Add more customizable ARGs with default values to Dockerfiles.

Simplify the testOnePeriod method.

Add TensorExpression

Make browserable C++ source code into HTMLs

fix protobuf size limit of seq2seq demo

Customized Paddle's document theme

config_parser增加新特性：支持同一个python文件内配置paddle

Re-design command options for testing for better understanding

add execute property by default for some top scripts

merge PaddlePaddle/Paddle

Conflicts:
	doc/conf.py.in
	doc_cn/conf.py.in
	doc_theme/static/css/override.css
	doc_theme/static/js/paddle_doc_init.js
	doc_theme/templates/layout.html

Auto compare cpu and gpu function.