Update MGET to be compatible with Copernicus Marine Toolbox 2.0.0

[jjrob]

Copernicus made a number of breaking changes. See https://help.marine.copernicus.eu/en/articles/9978784-what-s-new-in-the-pre-release-of-version-2-0-0-of-the-copernicus-marine-toolbox. We should verify that MGET still works.