relax SVN archive

Renamed the module to avoid a name clash.

Shifted all of the model-free optimisation related methods into a separate module.

Bug fix for the system test of AIC model selection between two diffusion tensors.

The diffusion tensor was not been properly set up.

Converted the grid_search() model-free method to the new relax design.

The grid_search_setup() method has been merged into this method.

Cleaned up the code of the overfit_deselect() model-free method.

Converted the overfit_deselect() model-free method to the new relax design.

Converted the select_model() model-free method to the new relax design.

Fixes for all the unit tests of the generic_fns.value.partition_params() function.

Added the missing import of the spin_loop.

The model 'm4' construction system test now passes.

Updated the docstring of the model_setup() model-free method to be in epydoc format.