relax SVN archive

Fix for the structure.pca user function front end.

The PCA name was misspelt as PCS.

Created the structure.pca user function front end.

This is currently modelled on the structure.rmsd user function framework.

Added a file to the test suite shared data to help implement the PCA structural analysis.

This is the N-domain of the CaM-IQ complex used in a frame order analysis. It is the first 5
structures from a call to the frame_order.distribute user function, with the different rigid-bodies
merged back together into a single molecule.

Updates to the Noe and Structure system test classes for the internal structural object changes.

The serial number can now be reset, and the chain ID information is no longer stored.

Modified the internal structural object to be less influenced by the format of the PDB.

The PDB serial number is now intelligently handled, in that it is reset to 1 when a new model is
created. This information is still kept for supporting the logic of the reading of the CONECT
records, and will be eliminated in the future.

The chain ID information is now no longer stored in the internal structural object, as this
information is recreated by the structure.write_pdb user function based on how the internal
structural object has been created.

Fix for spelling mistake and documenting the new behavior of relax_disp.r2eff_read(), when reading r2eff points with the same frequency.

If the spin-container already contain r2eff values with the 'frequency of the CPMG pulse' or 'spin-lock field strength',
the frequency will be changed by a infinitesimal small value of + 0.001 Hz.
This allow for duplicates or more of the same frequency.

Using Gary's lib.float.isNaN() instead of math.isnan(), to have backwards compability with python 2.5.

Added the svn:mime-type property as "application/octet-stream" to all bzip2 compressed files.

This is to avoid binary diffs.

The command used was:
find -iname "*.bz2" -exec svn propset svn:mime-type "application/octet-stream" {} \;

Added a sample script for back-calculating relaxation data from a model-free results file.

This is useful when the results file is not the final model, as these results file do not contain
the back-calculated data. This is in response to Christina Möller's sr #3303 support request
(https://gna.org/support/?3303).

Fix for GUI test: relax --gui-tests Relax_disp.test_paul_schanda_nov_2015 --time -d.

When loading from a script state file, the value of "None" can be present.
This is now set to the standard values.