relax SVN archive

Added some missing imports.

Updated the maths_fns package __all__ list.

Renamed the maths_fns.frame_order.frame_order_matrix_ops module to matrix_ops.

Shifted the maths_fns.pseudo_ellipse module to maths_fns.frame_order.pec.

Removed a pile of unused imports.

Spun out all of the frame order model specific code in frame_order_matrix_ops to separate modules.

Spun out the free-rotor and torsionless pseudo-ellipse target function code into their own modules.

Spun out all of the pseudo-ellipse code from frame_order_matrix_ops into the pseudo_ellipse module.

Completion of the changes of r17321.

The frame_order and frame_order_matrix_ops modules have been shifted into the new
maths_fns.frame_order package.

Shifted the frame order target function code into the new maths_fns.frame_order package.

This will allow for a better organisation of the code and the splitting up of the far too large
frame_order_matrix_ops module.