fix infer class_num bugs in release/2.0-beta branch

* Fix a link error

* Fix some bugs in "Resume Training"

* Amend a detail about "Resume training"

* Add English version of getting started.

* Create regnet.py

* Update __init__.py

add pre-label function

fix readme

fix readme png

fix getting started

Some updates

This reverts commit 17c66f42.

The bug had been fixed by another way.

fix typo

cherry-pick add hs-resnet coming soon

add ghostnet and modify shufflenet

fix load ckp

fix effnet import

fix cpu train

fix quick start code and doc