The grid_bounds() function has been renamed to grid_setup(), and it now accepts and processes the
inc user function argument. The error checking code of the relaxation curve-fitting
grid_search_setup() optimisation function has been shifted into this analysis independent
grid_setup() function to shift the minimise.grid_search user function error checking out of the
specific analyses. The function now scales the parameter bounds, using the yet-to-be implemented
scaling() method of the parameter object. And the grid search increments are converted into a
per-model list of lists.
