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[jbolns]

Large PR with breaking changes.

• Full codebase re-structuring.
• KWARGs now contain all configuration settings needed across the entire process.
• Segment-based mathematical beams.
• Twin cube look-ahead feature to catch risk failures in time to avoid them
• Preliminary .bgraph write function, currently being tested only on a couple example files.

A few rough corners left will need revisiting after migrating to AugmentedNXGraph. No point in doing much about these until everything is unified under a single data structure

• Accuracy of twin cube ID tracking will need to be confirmed once a final rationale emerge
• Multi-beam clashes still rely partially on an array but need to be transferred to a fully mathematical approach
• Cube classes are still very much necessary

Closes #31