Add shape of earth 1 and 7

This PR extends `ellispsoid` to handle `shapeOfTheEarth` value `1` and `7`.

This is a precursor to GDT 4/5.
Probably should say 'iterable' here, rather than ndarray, as that is the actual distinction it makes (and it does work for lists etc.) -- but leave as 'ndarray' in the return spec.