SNAP-3518 clone Datum when transferring GcpGeoCoding

[lveci]

https://senbox.atlassian.net/browse/SNAP-3518

clone Datum when transferring GcpGeoCoding

[TomBlock]

Hi Luis,

instead of copying the Datum, I'd prefer that you implement the clone() method of the Datum class and use this in GCPGeoCoding.clone(). There exists already a (useless) stub in Datum.

Can you please add the STTM annotation at the GCPTest method you updated?

Cheers, Tom

[CLAassistant]

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