Kliff DNN torch trainer

[ipcamit]

Summary

Added tests and trainer for training generic dense neural networks using libdescriptor and pytorch (as opposed to lightning).

• Batched descriptor evaluation
• DNN model using TorchML driver

TODO (if any)

• Need to add the capability to write the trained model as a valid DUNN driver model.

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[mjwen]

Looks great! Merged.