relax SVN archive

Renamed __generate_object_from_pdb() to __fill_object_from_pdb() and changed its behaviour.

The method no longer returns a Structure_container instance but simply fills out the one
corresponding to the model.

Wrote a unit test for the Internal.__parse_pdb_record() method.

Fix by renaming of the Structure_container.__init__() method.

Fix for the initialisation of the Structure_container object.

The object variables were not being placed into self.

Fix for the unit test of Internal.load_pdb().

Updated the atom_add(), atom_connect(), and terminate() API base class methods for the model arg.

Updated the terminate() method to handle multiple models.

Updated the atom_connect() method to handle multiple models.

Updated the atom_add() method to handle multiple models.

Wrote the load_pdb() structural API method for the internal relax object.

This involved the addition of the following private methods:
__generate_object_from_pdb
__parse_models
__parse_pdb_record