[Multithread] Implement the NOT discriminant.

[AndreaCatania]

Implement the NOT discriminant that will allow two systems to run in parallel even if they fetch the same components:

void system_1(Query<Comp1, Comp2, Not<Comp3>>  &p_query){}
void system_2(Query<Comp1, Not<Comp2>, Comp3>  &p_query){}

Even if system_1 and system_2 are fetching Comp1, the Not filter prevent the query to collide, so both can run in parallel.

[AndreaCatania]

Moving the proposal to discussions to keep the issue just for things to fix.