relax SVN archive

Full errors are raised in the protected_exec() function if in debugging mode.

Improvements to the structure.vector user fucntion docstring.

Implemented the structure.vectors GUI user function and menu entry.

Fixes for the new spin_control() method.

Docstring fix for the spin_control() method.

Created the wizard page spin_control() method for adding a spin control.

Modified the messages for missing unit vectors in the model-free auto-analysis tab.

Fix for the grace.view user function GUI page - the directory is set to None.

Without this, the directory would be set to 'grace' and prepended to the absolute path of 'file'!

The results file viewer is now executing the grace.view user function to display Grace files.

Another attempt at error handling.

This should now provide the correct behaviour by not showing tracebacks in standard mode.