relax SVN archive

Wrote a unit test for the model-free duplicate_data() method for single mf models.

Fix for the structure duplication in duplicate_data().

Fix for the test_duplicate_data_fail1() unit test.

The attribute modified didn't exist, so the test was failing.

Wrote a unit test for catching the failure of the model-free duplicate_data() method.

This happens when the structures are different.

Added code to duplicate the structural object if it doesn't exist in the new pipe.

This has been added to the model-free duplicate_data() method.

Added a few checks to test_duplicate_data3().

Wrote another unit test for the model-free duplicate_data() method.

Fixed the model-free duplicate_data() unit tests.

Added a test for the model_index arg in the duplicate_data() method.

Fix for the model-free duplicate_data() method for when the data pipe is empty.