Add methods to check the disjointness between classifiers

[claudenirmf]

Given two (or more) classifiers, evaluate whether they are disjoint. Disjointness checks between more than two classes, if necessary, must be clear about the implementation (i.e., pairwise or overall disjointness).

areDisjoint(classifierA : Classifier, classifierB : Classifier): boolean;
areDisjoint(...classifiers : Classifier[]): boolean;
arePairwiseDisjoint(...classifiers : Classifier[]): boolean;

[claudenirmf]

Also, this method must check orthogonal hierarchies among its ancestors, and consider the disjointness of generalization sets, ultimate sortals, and ontological natures.