Fuselage synthesis

[Czarified]

Finally rolling in a functional Fuselage Synthesis routine! This marks the first minor version release!

This has taken way too long, but I've got a working example script building and analyzing a Fuselage component. I like the data structure and execution speed. The accuracy isn't there yet, but now that all the pipes are connected, we can work on that in the future. I've left several TODO comments in the source files to keep track of this when the time comes.

This effort took significant refactoring and new class definitions. Some highlights:

1. Loadcases are now a dedicated class with general definitions to contain all the potential input data that an aircraft flight case would need, to generate structural loads. This isn't complete, but some methods like panel flutter need the Mach and Altitude directly. They get these from the Loadcase object.
2. Construction type support is limited right now to Longerons. These are primary style I'm interested in, and stringer construction is harder to calculate anyway. If stringer types are defined, they should raise NotImplementedErrors.
3. The Fuselage class contains attributes for the relevant component models. So cover_model, frame_model, long_model are attributes of Fuselage and must be defined from instantiation. This isn't locking in the sizing of these, just the object they can reference. Materials and other sizing attributes can and are changed as part of the synthesis routine.
4. Net Loads methods on the Fuselage are able to generate a Shear-Bending diagram and look up the fuselage loads at any arbitrary station by linearly interpolating on this diagram (the Fuselage.lookup_loads() method).

There's more updates but I'll leave it here. No one reads these except for me anyway. 😁