Allow for discarding of non-max projections

For a faster, more greedy and inaccurate search for maximal reductions allow via yet another option to directly skip non-maximal projections at each recursive steps (use pleq instead of peq in ProjectionSet.has()), and in getViableProjections (on top of unique remove also rows with pleq, or re-implement to fully use ProjectionSet).

In terms of "greediness level", starting with the least greedy, the suggested order of switching off options would be: backtracking (default false), then non-max projections (default true), then recursive search (default true).