* add multi xpu support for PaddleClas about dygraph

* add dygraph multi xpu support

* fix repvgg eval

* fix dp training

* fix single card train

* add find_unused_parameters param

* fix default val

* Support Visual DL

* Fix VDL

* Add doc of VDL, test=document_fix

* Add the en doc of VDL, test=document_fix
Co-authored-by: Nlittletomatodonkey <2120160898@bit.edu.cn>

* fix eval script

* fix dali shell

* add support for multi cards eva

* fix local rank
* fix export model

* unify model and model_name

* rm unsed archs fix bug of se_resnext

* fix distillation model for distributed.launch

* fix export model for googlenet

fix log benchmark

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

polish codes and docs to adapt Paddle2.0-rc