Add option of auxiliary wavelengths resonating in arm cavity and related calculations
Since Arm Length Stabilization (ALS) is an important part of ifo design and requirements, it would be nice to allow adding auxiliary wavelength(s) that are assumed to be circulating in the arm cavities. The helper function arm_cavity(ifo) can be expanded to calculate cavity parameters for the auxiliary wavelengths. This could be the start of supporting the calculation of noise contributions to auxiliary wavelength loops as well. I believe there is more potential for development once we have the wavelengths as an ifo parameter.