ONNX i/o

[mschrimpf]

From Ko:

I was wondering whether you have considered the ONNX format (https://onnx.ai) for dealing with neural network models built on various different platforms. This is the open neural network exchange format especially built for interchangeable AI models built on almost any platform (PyTorch, tensor-flow, Caffe etc). This has been developed by Microsoft and Facebook. It seems fairly simple to convert any existing model built on any of these platforms to ONNX format and share it with others (who might not be using the same platform for their own model development endeavors).

I was thinking may be for simplicity at our end — we can make it mandatory to convert every model to the ONNX format before submission.

Having ONNX I/O (import/export) is probably a good idea once we want to release mapped brain-models.