relax SVN archive

Continued the implementation of the reading of the generic peak intensity file.

The good file is now input.

Reverted revisions 8096 and 8097.

The command used was:
svn merge -r8097:8095 .

This follows a discussion started by Edward d'Auvergne at:
https://mail.gna.org/public/relax-users/2008-12/msg00000.html
(Message ID: 7f080ed10812030146w7e73ce24r75d32121e5f1c05f@...)

Added a sample script for the creation of the PDB representation of the XH bond vectors.

The centre_of_mass() function now only throws warnings rather than RelaxErrors.

This allows the CoM to be calculated even if a few elements are unknown or if the element record is
missing.

Fix for the centre_of_mass() function.

When no element entry is present in the PDB file, a RelaxError is thrown.

Bug fix for the centre_of_mass() function.

The spin id string is now created to correctly return the molecule, residue, and spin containers.

Removed the PyMOL execution commands from the XH bond distribution PDB representation system test.

Another bug fix for the create_vector_dist() function.

This time the atom number was not being incremented for chain B so that there are multiple atoms of
the same number in the PDB file.

Bug fix for the create_vector_dist() function.

The chain B of symmetry vectors was exactly the same as chain A and not mirrored.

Bug fixes for the PyMOL cartoon() method.

As with the open_pdb() method, cartoon() was not handling the structural object correctly and was
not handling multiple structures.