relax SVN archive

Implemented the backend of the structure.mean user function.

This primarily occurs within the internal structural object in the new mean() method. The
pipe_control.structure.main.mean() function simply checks if the current data pipe is correctly set
up and then calls the structural object mean() method.

Some fixes and additional checks for the Structure.test_mean system test.

Import fix for r26099.

Converted all of the pipe_control.strucuture.main functions to use the check_structure() object.

This standardises and improves all of the checks.

Created the pipe_control.structure.main.check_structure() checking object.

This will be used for providing much more detailed feedback for when structural information is
missing.

Fixes and simplifications for the pipe_control.pipes.check_pipe() checking object.

One of the RelaxError classes were not initialised and the docstring was incorrect.

Implemented the structure.mean user function frontend.

The backend is currently just a stub function.

Created the Structure.test_mean system test.

This is to test the functionality of a planned new feature, the structure.mean user function. This
is an analysis aid that will calculate the mean structure from all loaded models.

Implemented counting of outliers for statistics.

This is to get a better feeling why some statistics are very much different between NI.

Task #7826 (https://gna.org/task/index.php?7826): Write an python class for the repeated analysis of dispersion data.

Improvements to the summary table for the frame order auto-analysis.

The rotor and free rotor model motional eigenframe parameter axis_alpha is now being converted into
spherical angles and reported in the table. This allows the motional eigenframe of all models to be
easily compared in the table.