relax SVN archive

Proper bug fix for the spin ID metadata lookup table pruning.

The Mol_res_spin.test_prune_metadata system test now passes. The previous fix of r18232 was not
complete, and it should have been in the spin_id_variants_elim() function rather than
metadata_prune().

Added some more checks to the Mol_res_spin.test_prune_metadata system test to demonstrate more bugs.

Bug fix for generic_fns.mol_res_spin.metadata_prune().

Non-unique molecules and residues are now removed from the spin ID lookup table.

Created the Mol_res_spin.test_prune_metadata system test to catch a bug in the spin ID lookup table.

Spin IDs appear not to be correctly removed from the lookup table.

Created the Pcs.test_load_multi_col_data2 system test to catch a bug with the molecule name.

This is the same as the Pcs.test_load_multi_col_data system test but the spins have the molecule
name set.

Created the Pcs.test_grace_plot system test to check the pcs.corr_plot user function.

Bug fix for the loading of PCS data from a file with different spin types in different columns.

This was caught by the Pcs.test_load_multi_col_data system test which now passes.

Added some printouts to the Pcs.test_load_multi_col_data system test.

Created the Pcs.test_load_multi_col_data system test to demonstrate a failure of PCS data loading.

This is a problem when 15N data is in one column and 1H data is in another, and the spin_id argument
is used to specify which is which.

Python 3 fix for the new pcs.structural_noise user function.

There was a string/unicode problem in the Grace plot creation code.