Add stability-constrained examples

[kanekosh]

Description of feature

Add examples and documentation of analysis/optimization with stability derivatives. It requires nesting OM problems. Reference: https://github.com/OpenMDAO/RevHack2020/tree/master/problems/oas_stability_derivs

Also, the origin for the chordwise coordinate should be documented. I believe the default origin is at LE for rectangular wing and nose for CRM, but I should double check.

Potential solution