Sort the experiments of a design of experiments
S = scidoe_string(D)
a m-by-nbvar matrix of doubles, the design of experiments.
a m-by-nbvar matrix of strings, the design of experiments.
Ignores the signs of the entries in D, and remove duplicate entries. Then replaces each entry equal to 1 by a "*".
In a DOE which has {0,-1,+1} entries, this factors the blocks which have +-1 entries. This makes the factorial blocks of the design more obvious.