Removed all instances of the GeneralizableValue attribute -- after inspecting the IL generated by the compiler for these, it turns out that using this attribute isn't necessary for these values (and is, in fact, strictly worse).
Stubbed unit tests for remaining collections modules (with the exception of PriorityQueue, as it's not implemented yet).
Implemented the subset/superset operations on IntSet and IntMap. On IntSet, Subset works just fine but Superset fails a few of the test cases. The IntMap operations are only exposed internally (for now).