ACNet reimplement based on PaddlePaddle

Hi, we re-implemented ACNet based on PaddlePaddle, which is included in official models.

[models](https://github.com/PaddlePaddle/models/blob/develop/PaddleCV/image_classification/models/resnet_acnet.py)

[weight utils](https://github.com/PaddlePaddle/models/tree/develop/PaddleCV/image_classification/utils/acnet)

Nice work to ACNet!

