relax SVN archive

Added the 'parallax shift' measure to the structure.atomic_fluctuations user function.

The parallax shift is defined as the length of the average vector minus the interatomic vector. It
is similar to the angle measure however, importantly, it is independent of the distance between the
two atoms.

Description improvements and GUI layout fixes for the structure.atomic_fluctuations user function.

Clean ups and speed ups of the structure.atomic_fluctuations user function.

Duplicate calculations are now avoided, as the SD matrix is symmetric.

Implemented angular fluctuations for the structure.atomic_fluctuations user function.

This adds the measure argument to the user function to allow either the default of 'distance' or the
'angle' setting to be chosen. The implementation is confirmed by the
Structure.test_atomic_fluctuations_angle system test which now passes.

Created the Structure.test_atomic_fluctuations_angle system test.

This will be used to implement the mapping of inter-atomic vector angular fluctuations between
structures via a new 'measure' keyword argument for the structure.atomic_fluctuations user function.

Another docstring fix for the Structure.test_atomic_fluctuations system test.

Docstring fix for the Structure.test_atomic_fluctuations system test.

Updated the Structure.test_atomic_fluctuations_gnuplot system test.

This is for the changes of the gnuplot correlation_matrix() plotting API function used by the
structure.atomic_fluctuations user function.

Forced the gnuplot correlation_matrix plot to be square.

This is for the correlation_matrix() plotting API function used by the new
structure.atomic_fluctuations user function.

Fixes and improvements for the gnuplot correlation_matrix() plotting API function.

This is for the structure.atomic_fluctuations user function. The "pm3d map" plot type is incorrect
for such data type, so instead of using 'splot', 'plot' is being used instead. The resultant EPS
file is now much smaller. The colour map has also been changed to one of the inbuilt ones for
higher contrast.