relax SVN archive

Removed some dud arguments to the model_loop() generator.

Wrote the model-free model_loop() generator method.

Docstring and comment fixes for select_all_sims().

Shifted set_selected_sim() to the base class.

Updated the set_selected_sim() method.

Modified the select_all_sims() function to use the model_loop().

Propagation of the spin_id variable.

An important fix for the model-free minimisation code for the merged count_spins() function.

Another fix for the test_count_spins() unit test.

Fixed the test_count_spins() unit test.