relax SVN archive

Created the Structure.test_pca_observers system test.

This is for testing the new observer structures concept of the structure.pca user function.

Added support for 'observer' structures in the structure.pca user function.

This allows a subset of the structures used in the PC analysis to have zero weight so that these
structures can be used for comparison purposes. The obs_pipes, obs_models, and obs_molecules
arguments have been added to the user function front end. The backend uses this to create an array
of weights for each structure. And the lib.structure.pca functions use the zero weights to remove
the observer structures from the PC mode calculations.

A weighted mean structure can now be calculated.

This is for the calc_mean_structure() function of the relax library module lib.structure.statistics.
Weights can now be supplied for each structure to allow for a weighted mean to be calculated and
returned.

Expanded the Structure.test_pca system test checks to compare to the values from Gromacs.

Improved the graphs in the backend of the structure.pca user function.

The graphs are now clustered so that different models of the same structure in the same data pipe
are within one graph set. The graph header has also been improved.

Created an initial Structure.test_pca system test.

This executes the new structure.pca user function, and checks if data is stored in cdp.structure.

Updated the Gromacs PCA results for the newest Gromacs version (5.1.1).

Added the Gromacs PCA results for the distribution.pdb file.

This includes a script used to execute all parts of Gromacs and all output files.

The structure.pca user function now creates graphs of the PC projections.

This includes PC1 vs. PC2, PC2 vs. PC3, etc.

Modified the assemble_structural_coordinates() method to return more information.

This is from the pipe_control.structure.main module. The 'lists' boolean argument is now accepted
which will cause the function to additionally return the object ID list per molecule, the model
number list per molecule, and the molecule name list per molecule.