Simplify python wrapper generation

[mhvk]

(Partially inspired by an old issue I raised over at astropy/astropy#6073)

It is not obvious one always needs all erfa functions available, and at least the python wrappers could be auto-generated (especially with the new module level __getattr__).

Though in fact all that do not have a warning/error flag could just omitted altogether (i.e., one would call the ufunc directly).