relax SVN archive

Converted all the model_selection methods into module functions.

Removed the check of the recently deleted modsel_run arg.

Converted the model_selection() user function to the new relax design.

The back end code still needs to be converted.

Fixes for the gyromagnetic ratio setup.

Fix for the initialisation of the maths_fns.mf.Mf class.

Fixed the call to assemble_param_vector().

Comment fix.

Modified the assemble_param_vector() method to allow the parameter set to be given as an arg.

Spelling correction in a comment.

Changed all refs to 'cdp.diff' to 'cdp.diff_tensor'.