use apt install -y python-opencv to run flower dataset

* add normalize switch to box_coder_op

* add default prior box var

* update according to the review

add host_memory_profiling_cn.md

enable infer api with multi-threads

fix test error in fluid_benchmark.py

fix protobuf memory leak

Fix dangling pointer bug in paddle/fluid/framework/executor.cc

refine benchmark/fluid

Faster RecordIO Scanner

* Auto generate python api for polygon_box_transform op.

* Add unitest.

* Modify optimizer in new API to support more usecase

* Modify CMake to include only modified examples

fix build error on mac

Fix term core only

Fix single pserver transpile error after merging