Added some text to explain why test only J(0) is discussed whereas the script also calculated F_R2 and F_eta.
This was suggested by Edward d'Auvergne in a post at:
https://mail.gna.org/public/relax-devel/2012-09/msg00044.html
(Message-id: <CAED9pY9U46ga6_j245peX1ETNZc_Lw0f5cz+5xx5rGVhee29YA@...>)
