relax SVN archive

Bug fox for the generic_fns.mol_res_spin.return_spin_indices() function.

The selection object was using the wrong variable name, and the look up table fallback was always
on!

More print outs and better data loading checks in the dipole_pair user functions.

The relax_data.read user function now prints out all of the data read in.

This is to better inform the user that something has happened.

Lots of fixes for the model-free system tests.

Bug fix - the spin_id arg for the relax_data.read user function now actually does something.

This argument is passed into the pack_data() function, where it is used to match against the spins
matching each file line. Only if there is a match, is the relaxation data loaded for that spin.

The return_spin_from_selection() function now lists all matching spins in RelaxMultiSpinIDError.

Fix for the return_spin_from_selection() function for a bug introduced in the last commit.

The return_spin() and return_spin_from_selection() functions can now handle multiple spins.

It the 'multi' flag is supplied, then lists of spins (and associated data) will be returned, rather
than a RelaxMultiSpinIDError error raised.

Created the list_to_text() RelaxError system function for prettifying the output of RelaxMultiSpinIDError.

Expanded RelaxMultiSpinIDError to be able to print out a list of all the matching spin Ids.