Add ZgyUtils.alturl() for wrapping SDAPI.getSerializedContext(), as was done in the old ZGY. Implemented for C++, the Python Wrapper, and SdGlue.
Normally the SDAPI has significant overhead when opening a file. Applications that repeatedly open the same file will typically choose to cache the open SDGenericDataset. For distributed applications this is not possible. The new getSerializedContext() offers an equivalent functionality by serializing the metadata from an open file. A later open, presumably running on a different machine, can then use this serialized data to open the same file with practically no overhead.
This PR only exposes the new feature in OpenZGY.