Spanet

**Export**
To enable SPANet to be used outside of the python environment, we added an `onnx` export utility to allow for easy export to the onnx format which has run-times available for many languages. Please refer to this section of the documentation:

[https://github.com/Alexanders101/SPANet#exporting](https://github.com/Alexanders101/SPANet#exporting)

1. New configuration file format with more options on inputs and event topology.
2. Allow for several different inputs, including global inputs for additional context.
3. New Regression and Classification output heads for performing per-event or per-particle predictions.
4. Gated transformers and linear layers for more robust networks. Less hyperparameter optimization.

Original Release of code for reproducibility.