Restructured BloomFilter, added BloomSet.

Roadmap for Setup:
(1) manage BloomSet intersections for faster iteration;
(2) manage list of unit clauses with BloomSet;
(3) manage list of lhs terms [or not?].

Use
(1) instead of clauses() for Subsumes();
(1) instead of clauses_with() for RemoveSubsumed();
(1) instead of clauses_with() for Consistent(), LocallyConsistent();
(2) instead of unit_clauses() for PropagateUnits();
(3) instead of primitive_terms() for Consistent()
    [or create the set there locally?].