Implementation of builtin predicate `notIn`

[dyamon]

This might be a problem since we can't change how RDFox performs its materialisation.

Possible solutions are:

1. Find a way to encode the predicate using RDFox aggregates and/or builtin functions;
2. Create a predicate in (specifying its instances during role creation) and than use negation-as-failure to simulate notIn. Since in cannot be deduced anywhere using NaF should be equivalent to having normal negation.

[dyamon]

After reading the definition of notIn(x, y) is seems like

[it] holds when the first element is an element of the set given as second element.

Despite the unfortunate name, this is much easier to implement.

[dyamon]

Despite the informal definition provided by the paper, it seems that notIn really means "not in". With the latest commit we implemented the second option proposed here:

2. Create a predicate in (specifying its instances during role creation) and than use negation-as-failure to simulate notIn. Since in cannot be deduced anywhere using NaF should be equivalent to having normal negation.