relax SVN archive

Bug fix for the N-state model grid search when only alignment tensor parameters are optimised.

The algorithm for splitting up the grid search to optimise each tensor separately, hence massively
collapsing the dimensionality of the problem, was being performed incorrectly. The grid_search()
API method inc, lower, and upper arguments are lists of lists, but were only being treated as lists.

Modified the N_state_model.test_populations system test to test the grid search code paths.

This performs a grid search of one increment after minimisation, then switches to the 'fixed'
N-state model and performs a second grid search of one increment. This now tests currently untested
code paths in the grid_search() API method behind the minimise.grid_search user function. The test
demonstrates a bug in the N-state model which was not uncovered in the test suite.

Implemented the multiple molecule merging functionality of the structure.load_spins user function.

The argument has been added to the user function frontend and a description added for this new
functionality. In the backend, the pipe_control.structure.main.load_spins() function will now call
the load_spins_multi_mol() function if from_mols is supplied. This alternative function is required
to handle missing atoms and differential atom numbering.

Fixes for the Structure.test_load_spins_multi_mol system test.

The call to the structure.load_spins user function has also been modified so that all 3 spins are
loaded at the same time.

Created the Structure.test_load_spins_multi_mol system test.

This is to test yet to be implemented functionality of the structure.load_spins user function. This
is the loading of spin information similar, but not necessarily identical molecules all loaded into
the same structural model. For this, the from_mols argument will be added.

Modified the internal structural object backend for the structure.read_pdb user function.

The MolContainer._det_pdb_element() method for handling PDB files with missing element information
has been updated to use the Periodic_table.has_element() method to check if the PDB atom name
corresponds to any atoms in the periodic table. This allows for far greater support for HETATOMS
and all of the metals.

Added 4 unit tests to the _lib.test_periodic_table module for the Periodic_table.has_element() method.

Created the Periodic_table.has_element() method for the lib.periodic_table module.

This is used to simply check if a given symbol exists as an atom in the periodic table.

Bug fix for the structure.align user function for when no data pipes are supplied.

The compression level for results files can now be set in the frame order auto-analysis.

This is via the new argument results_compress_type, which is used to set the compress_type argument
of the results.write user function. The results reading parts of the auto-analysis have been
updated to allow uncompressed, bzip2 compressed, and gzip compressed files to be handled.