Implement interface to NIR

[kmheckel]

Create functions to load/save models to HDF5 under the Neuromorphic Intermediate Representation standard to facilitate cross-platform deployment.

https://nnir.readthedocs.io/en/latest/what.html

• Implement spyx.nir.to_nir()

• Implement spyx.nir.from_nir()

• Support feed-forward network import

• Support ConvNet import

• Support explicitly recurrent import

• Implement FFN exporting

• Implement CSNN exporting

• Implement RSNN exporting

[kmheckel]

See docs/examples/nir for notebooks documenting functionality and testing. Currently works for single neuron loading example, writing the model back is a work in progress.

[kmheckel]

Working on getting the weight scaling to function properly.

• Get weight scaling working so that loaded models function properly

[kmheckel]

Importing models is now supported but is likely somewhat brittle. Will require further testing. Export capabilities started but limited to FFN for now, rest is a work in progress.

[kmheckel]

This needs formal tests included into the library before closing this issue.