relax SVN archive

Updated the return_data() and return_error() base class methods to the new relax design.

Updated the base class method has_errors() to the new relax design.

Removed an orphaned comment.

Removed the empty __init__() method and shifted its docstring to that of the class.

Removed the empty __init__() method and shifted its docstring to that of the class.

Alphabetical sorting of the class methods.

Additions to the system test of the 5-state model in the xz-plane (no pivotting of alpha).

The 5-state model is now set up in the script.

Added the missing import of RelaxIntError.

Wrote the N arg unit test for the n_state_model.model() user function.

Wrote the n_state_model.model() user function for setting up the N-state model.