relax SVN archive

Bug fixes for the PyMOL open_pdb() method.

This method was not handling the structural object properly.

Bug fix for the create_vector_dist() function.

A structure needed to be added to the internal structural object.

Converted the symmetry flag to a bool.

A number of fixes for the create_vector_dist() function.

Added the missing spin_loop() import.

Added a system test for the creation of an XH bond vector distribution.

This test mimics the script used to create figure 7.8 of my PhD thesis
(http://eprints.infodiv.unimelb.edu.au/archive/00002799/).

Fix for bug #12670 (https://gna.org/bugs/index.php?12670).

This bug was reported by Michael Funk (mifu att nmr dot mpibpc dot mpg dot de).

The problem was that the relaxation curve-fitting return_error() method was returning the global
cdp.sigma_I error structure - which does not exist for all error types - when it should have been
returning the spin specific error structure.

Activated the system test catching bug #12670 (https://gna.org/bugs/index.php?12670).

This bug was reported by Michael Funk (mifu att nmr dot mpibpc dot mpg dot de).

The script for reproducing bug #12670 (https://gna.org/bugs/index.php?12670) now works.

This bug was reported by Michael Funk (mifu att nmr dot mpibpc dot mpg dot de).

Added all the files necessary to reproduce bug #12670 (https://gna.org/bugs/index.php?12670).

This bug was reported by Michael Funk (mifu att nmr dot mpibpc dot mpg dot de).

The script needs to be modified to point to the correct locations and needs to be activated as a
system test.