Adds mapping layer for PVHandler (#481)

- Adds method to PLVHandler for reindexing via remapping.
- Adds an option to PLVHandler to reindex via remapping or copying.
- Adds updates to the sDAG clade maps so that clade maps are also used for finding grafted node neighbors (previously only for host nodes).

extras/benchmark.cpp

@@ -85,10 +85,6 @@ std::set<Bitset> BuildAllSubsplits(size_t n) {
 }
 }  // namespace SubsplitSetBuilder
 
-void Test1(int argc, char* argv[]) {}
-
-void Test2(int argc, char* argv[]) {}
-
 int main(int argc, char* argv[]) {
   Stopwatch timer(true, Stopwatch::TimeScale::SecondScale);