[Ifeffit] max number of restraints

[Matt Newville]

Hi Victor,

As Bruce said, the limit of 10 restraints is compiled-in.  It could
certainly be increased.

But I'm impressed that you have more than 10 independent restraints to
impose!   Depending on the nature of your restraints, it might be
possible to combine some of them.  That is, using one restraint of

   restraint_sum = (restraint1) + (restraint2) + (restraint3)

(where each restraint might be an elaborate calculation)  is only
different from using three restraints if the three restraints are
strongly anti-correlated, so that they compete against one another.
If you're restraining different bond lengths, some of them probably
can be combined.

It's definitely better, and more elegant, to use multiple restraints,
but I think the mathematical distinction may be pretty small.

--Matt