1st parameter = constraint # (except for none) 
    <LI>
    2nd parameter = style of that constraint 
    <LI>
    3rd-Nth parameters = coeffs 1 to N-2 
</UL>
<PRE>
styles:
</PRE>
<UL>
    <LI>
    none = erase all constraints and all atom and bond assignments 
    <LI>
    setforce = set force on each atom in group 
    <LI>
    addforce = add a force to each atom in group 
    <LI>
    aveforce = apply an external force to group of atoms such that every 
    atom is accelerated the same 
    <LI>
    res