Add support for Gateway Extension APIs

**System information**

- Are you willing to contribute it (Yes/No): Yes

**Describe the feature and the current behavior/state.**

Currently the create, update, attach, detach, audit, validate and signing APIs are supported by the SDK. It would be useful for the SDK to support the export and transfer APIs as well

**Will this change the current API? How?**

It will add new calls to the SDK interface that will allow use of the export and transfer APIs

**Who will benefit with this feature?**

Any user that may want to invoke export and transfer from the SDK