relax SVN archive

Added a unit test to bounce around all the conversion functions in maths_fns.rotation_matrix.

This bounces through:
1) euler_zyz_to_R().
2) R_to_axis_angle().
3) axis_angle_to_quaternion().
4) quaternion_to_axis_angle().
5) axis_angle_to_R().
6) R_to_quaternion().
7) quaternion_to_R().
8) R_to_euler_zyz().

Created the maths_fns.rotation_matrix.R_to_quaternion() function.

This is accompanied by 2 unit tests.

Created the maths_fns.rotation_matrix.quaternion_to_axis_angle() function.

This is accompanied by 2 unit tests.

Created the maths_fns.rotation_matrix.axis_angle_to_quaternion() function.

This is accompanied by 2 unit tests.

Huge simplifications to the unit tests for the maths_fns.rotation_matrix package.

Alphabetical reordering of functions.

Function renaming and argument order changes in the maths_fns.rotation_matrix module.

The naming scheme is now more logical (as well as the argument order).

Added another unit test for maths_fns.rotation_matrix.R_axis_angle().

Bug fix for R_to_axis_angle().

All vector elements were NaN when the angle is 0. Now the zero vector is not normalised by zero.

Added a unit test for maths_fns.rotation_matrix.R_to_axis_angle() using R = I.