relax SVN archive

Added the NMR model number to the collection of structural attributes stored as lists.

The load_pdb() structural method now accepts the struct_index arg.

This is passed in by from_xml() to place the structure in the correct position.

Modified from_xml() to handle multiple loaded structures.

Modified the structural API base class __init__() method.

This is to prepare for the tidying up of the structural object to better handle multiple structures.

Propagation of the results file directory all the way through to the structure reading code.

Updates to the test_load_results() system test.

Moved some files around to let a system test pass.

Improvements to the from_xml() method.

The load_pdb() method now returns True if the file was loaded or False otherwise.

Removed the RelaxNoPDBFileWarning warnings.