Shift of the GUI calculation code to using the relax API (rather than scripting).
This corresponds to one component of the patch_II file attached to https://gna.org/task/?6847 by
Michael Bieri (https://gna.org/users/michaelbieri). See the thread starting at
https://mail.gna.org/public/relax-devel/2009-11/msg00045.html, specifically the details in
https://mail.gna.org/public/relax-devel/2009-11/msg00056.html.
This includes a large rearrangement of the model-free code, which could not be separated from the
shift to the relax API.
