Dev/misc paper updates

[nickkamp1]

This branch includes many updates that get the codebase ready for the first paper. These include

• Removing hard dependence on DarkNews (now optional)
• Fixing serialization routines for the new injector class and making sure we can actually save and load injector objects
• Updating the controller object to be able to reweight previously generated events to new physical distributions
• Make it possible to serialize vectors of interaction trees
• Make a number of updates to the paper plot notebooks to get figures ready for the paper
• Some renaming of objects for coherence
• Make it possible for the Weighter objects to use different interaction collections for the injection and physical processes
• Add hyperk

Remaining tasks:

• Make sure serialization of injectors works when they include a pyDarkNews[] object, I don't think this currently works
• Fix serialization for TreeWeighter, currently experiencing compilation errors

This PR is probably now ready for review, we should merge and submit the paper!