relax SVN archive

Renamed load_structures() to load_pdb() in the Scientific python PDB structural object.

Changed a few method names in the API base class.

load_structures() is now load_pdb() and write_pdb_file() is now write_pdb().

Modified the unit tests to call Internal.load_pdb().

Updated the internal relax structural object unit tests to test this object.

Copied the Scientific python unit tests for the internal relax structural object unit tests.

Import fixes for the newly renamed generic_fns.structure.internal() module.

Module rename.

Started the conversion of the internal relax structural object to be independent of the PDB format.

Corrected a small error in a 'for' loop that prevented relax from working.

Started to convert sel_spin() to the new design.