User guide - aerodynamic guidance

[DominicDirkx]

The pages from the old website (http://tudat.tudelft.nl/tutorials/tudatFeatures/accelerationSetup/aerodynamicGuidance.html) on aerodynamic guidance need to be thoroughly updated and moved to the new website, with a change to Python, of course. Some the of info from the old website is now/will go into the API, making this page somewhat cleaner.

Points that need to be highlighted:

• Defining body angles, and relation to other definitions of body-fixed frames
• Combined use of aerodynamics and thrust (on a different page?)
• Use of aerodynamic coefficient interface
• Use of control surface deflections

In addition to documenting, this step should also include a modification of the interfaces for aerodynamic guidance: removing the need for a specific derived class, and instead moving to the use of custom guidance functions (as is the case for all other custom models).

[DominicDirkx]

This is now in this pull request: #71