Bug fix: Added the function __deselect_spins() to remove spins with too little data.
This fixes bug #14428 (http://gna.org/bugs/?14428) reported by Pierre-Yves Savard <pierre-yves dott
savard at bcm dot ulaval dot ca>.
The new function is almost identical to that used in the model-free analysis performed by relax in
that spins with no or too little data, or those which would be over-fit are removed from the
analysis.
