Add LambdaNetworks support

[jxtps]

Introduced in https://openreview.net/forum?id=xTJEN-ggl1b discussed in https://www.youtube.com/watch?v=3qxJ2WD8p4w with tensorflow implementation in https://github.com/g0lemXIV/LambdaNetworks and pytorch implementations in https://github.com/lucidrains/lambda-networks and https://github.com/leaderj1001/LambdaNetworks - LambdaNetworks are an interesting new development in deep learning for image processing:

It would be very interesting to have LambdaNetworks be a part of the classification_models, thanks!