Sort the experiments of a design of experiments
D = scidoe_sortdesign(D)
a m-by-nbvar matrix of doubles, the design of experiments.
Sorts the rows of a DOE, so that we gather the rows which are common, ignoring the signs of the entries.
In a DOE which has {0,-1,+1} entries, this gathers the blocks which have +-1 entries. This makes the factorial blocks of the design more obvious.