adding ge kretz 2d data access

[gordon-n-stevenson]

Hi 👋

We've been using the 2d image classes in itkultrasound to resample polar 2d data from a ge voluson system. Keen to share and add this IO functionality. It seems better to extend itkultrasound than build another module would this be sensible?

Happy to put a pull request together

[dzenanz]

Yes, of course! Contributions are welcome. Remote modules generally follow the same contribution process as the main ITK repository.