relax SVN archive

Fix for the model-free _determine_model_type() method.

This should skip deselected spin rather than spins without relaxation data!

Converted the Rdc.test_rdc_load() system test to the interatomic data design.

Converted another test suite RDC data file to the interatomic data design.

Fix for the rdc.read user function - values and errors of None in the file are supported again.

This was broken with the interatomic data redesign.

The relax_io.read_spin_data() function can now handle spin IDs in quotes.

Fixes for 3 of the Structure system tests for the interatomic data design.

The Scientific Python structural object are_bonded() now uses 2.0 Angstrom as a cutoff radius.

Converted all of the Unit_vectors system tests to the interatomic data design.

Added the are_bonded() and get_molecule() methods for the Scientific Python PDB reader.

This is now needed for defining interatomic vectors in the interatomic data design.

Some more fixes for the N_state_model.test_stereochem_analysis system test.