Re-add Encrypt/Decrypt Cipher Update and Finish

To keep the scope of this example and the tests limited, we decided to remove the C_EncryptUpdate und C_EncryptFinal and the corresponding Decrypt functions from the current implementation and instead have a proper keyHandle support as described in #5 implemented and tested.

To not forget it, we add an issue to re-add it, with proper sample and tests, in the future. 