IsNilpotentFreeNearring( nr )  
A near-ring N is called nilpotent free if its only nilpotent element is 0.
The function IsNilpotentFreeNearring checks if 
0 is the only nilpotent and returns the according boolean value 
true or false.
gap> IsNilpotentFreeNearring( LibraryNearring( "V4", 22 ) ); true
GAP 3.4.4