relax SVN archive

Deleted the __init__() class methods as these were empty, and shifted the docstring to that of the class.

The test_write_read_pipes() system test is now using the VALID_TYPES module variable to get all pipes.

Shifted the valid types private function variable into a module variable.

Wrote a system test for the writing and re-reading of data pipes.

Renamed the data pipes system tests module.

Added a unit test to check if all the maths_fns.kronecker_product.transpose_*() functions revert.

Calling the function twice should return the matrix to the original state.

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.