Add functionality to make individuals of given class distinct

[csnyulas]

There is a menu item that allows one to assert that all individuals in an ontology are distinct:
Edit -> Make all individuals distinct....
This is very useful, but often it would be more useful to make the individuals of a certain class distinct among each other, rather than all individuals in the ontology (as it is the case in this user request).

We could add such a functionality as an additional menu item in the Edit menu, or, even better, in the context menu in the Classes tree, or both.

We could add this also to the Individuals by type view, where one could select multiple classes and make the instances of those classes different. Either as a single set of distinct individuals including the instances of all the selected classes, or multiple sets of distinct individuals each of those containing the instances of each of the selected classes.