relax SVN archive

Split generic_fns.selection.exists_mol_res_spin_data() into 4 new functions.

The new functions are:
exists_mol_res_spin_data()
exists_mol_data()
exists_res_data()
exists_spin_data()

Big bug fix for the generic_fns.residue.create() function.

The mol_to_cont was being set to a ResidueContainer rather than a MoleculeContainer!!!

Bug fix to the return_residue() and return_spin() functions.

When a residue or spin is not identified, then this should correspond to all residues or spins and
not none!

Added 2 unit tests for the generic_fns.selection.return_spin() function.

Added the missing import of RelaxNoSpinError.

Fixes for the unit tests of generic_fns.selection.generate_spin_id().

Bug fix for the generic_fns.selection.generate_spin_id() function.

The residue and spin names now always start with the identifier ':' or '@'.

Added some more missing imports.

Converted specific_fns.relax_data.update_global_data_structures() to the new relax design.

Bug fix for the read() function.