add tune example

[laurencejackson]

Add a tune example usign Ax and Ray

ax with ray: https://ax.dev/tutorials/raytune_pytorch_cnn.html
mlflow with ax: https://github.com/mlflow/mlflow/tree/master/examples/pytorch/AxHyperOptimizationPTL

NAS
https://pytorch.org/blog/effective-multi-objective-nueral-architecture/