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.
As I am a bear of very little brain, please could you explain why we have a (growing) bunch of optional parameters here? These parameters aren't passed in either of the calls to this function. :confused: