add mkldnn config

* unify model and model_name

* rm unsed archs fix bug of se_resnext

* fix distillation model for distributed.launch

* fix export model for googlenet

add hub serving code and doc

* add densent init

* fix export model

fix python and cpp inference

fix feature map visualization

fix log benchmark

1. fix dist training 
2. fix cpp infer to support dir inference

polish codes and docs to adapt Paddle2.0-rc

add pre-label function

This reverts commit 17c66f42.

The bug had been fixed by another way.