relax SVN archive

Added a unit test for the private Scientific_data.__molecule_loop() method.

Added a unit test for the Scientific_data.atom_loop() method.

Added some checks to the test_load_structures() unit test.

Fix for the load_structures() method, the model arg should be a keyword arg.

Started the replacement of the use of tokenise() by the full selection object.

Fix for the test_load_structures() unit test.

Shifted the 'test.pdb' file into the directory for data shared between the system and unit tests.

Added the framework for the unit tests of the Scietific Python PDB structural object.

Included is a test of the load_structures() method.

Added the _structure directory to the __all__ list.

Added the directory for the unit tests of the generic_fns.structure package.