initial port over of limb darkening search code
modifications limb darkening lookup to work with OECPy
modified limb_darkening code to require a wavelength not a wlgrid and added some test code to example
prefixed functions with their modules
find nearest code
limb darkening code runs but without validation
tidy limb darkening code
lookup works but find nearest seems wrong
added unit tests for find_nearest
working limb_darkening coeff lookup code - change default wl to 1.22 (no interp)
Merge branch 'feature/limb_darkening' into develop