## Summary
* Changed the office LAN convenience function to a class with a registry. Now, plugin can register custom node adders.
* Added ability to define `node_sets` in the config that map to `NetworkNodeAdder` subclasses
* Made airspacefrequency into a DTO class again to make management simpler.
* Moved the node registry out of `HostNode` and `NetworkNode` into `Node`
* Changed game.py to check the hardcoded node types before the node registry (this will change once I add ConfigSchema to all node subclasses)
* Made `show` method of the network container show all nodes, including ones registered at runtime.
## Test process
* Existing tests passed.
* Added unit tests for node adders
## Checklist
- [X] PR is linked to a **work item**
- [X] **acceptance criteria** of linked ticket are met
- [X] performed **self-review** of the code
- [X] written **tests** for any new functionality added with this PR
- [X] updated the **documentation** if this PR changes or adds functionality
- [ ] written/updated **design docs** if this PR implements new functionality
- [X] updated the **change log**
- [X] ran **pre-commit** checks for code style
- [ ] attended to any **TO-DOs** left in the code
8419fd751a