relax SVN archive

Created the Selection.contains_mol() method.

This is for testing if a molecule name, in string form, is contained in the selection object.

Wrote a unit test for the Scientific_data.__molecule_loop() method with a non-matching selection object.

Wrote a unit test for the private Scientific_data.__molecule_loop() method with a selection object.

Fix for the __molecule_loop() method.

Molecule names of None are now caught.

Added some checks to the test___molecule_loop() unit test.

Fixes for the __molecule_loop() method.

The selection object is now used for comparisons.

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.