Add new function, NAND, designed to create a composed predicate representing the logical NAND operation
applied to a list of predicates. The NAND operation is a logical operation
that returns true only if all perdicate result in false otherwise false
Add new function, Xnor, designed to create a composed predicate representing
the logical Exclusive NOR (XNOR) operation applied to a list of predicates.
The XNOR operation is a logical operation that returns true only
if all operands have the same boolean value