Use theta for geometric twist angle and delta for trailing edge deflection angle

[1-Bart-1]

• theta is the angle between panel chord and body frame x-axis around the local spanwise panel y-axis, does not depend on the apparent wind, and can be used to describe the "twist" or deformation of the kite body
• delta is the angle between the deflected trailing edge and the panel chord, around the panel spanwise y-axis
• discuss and agree if this is a good plan
• add to documentation
• rename arguments in functions
• update docstrings

similar use of delta for flap deflection: https://aviationdose.com/wp-content/uploads/2020/01/Fundamentals-of-aerodynamics-6-Edition.pdf
similar use of theta for twist angle: https://arc.aiaa.org/doi/10.2514/1.G001663

[ufechner7]

Why do you want to rename lambda to delta ?

Current definitions: https://albatross-kite-transport.github.io/VortexStepMethod.jl/dev/glossary/

[1-Bart-1]

Because delta is the convention for the flap deflection angle, which is similar to trailing edge deflection. Is lambda based on any convention / literature?

[ufechner7]

OK, go ahead with delta.

[ufechner7]

I updated glossary.md. @1-Bart-1 can you continue with update the code and the doc strings?

[1-Bart-1]

will do