Option to Import ONNX models

[akhilg206]

It would be great if we could add option to load ONNX models and try out training them. I do suspect that not all models maybe directly importable but worth trying

[pbrownMW]

Makes sense!

For import from TensorFlow or PyTorch, this can be done easily in Deep Network Designer. That could be accessed by choosing Build Network, ignoring the template layers, and doing the import there.

I think ONNX import would be straightforward to implement in this app using importNetworkFromONNX. In the simple case, use uigetfile to let a user select a .onnx file, call importNetworkFromONNX(onnxFile) and import that. There would be some cases where setting options to the function would lead to a better import; that would require a more complicated custom dialog.

Leaving open as this seems tractable to do.