Support Multi-query Motion Planners like PRM and PRMStar

[WaterHyacinthInNANHU]

Hi! Have you considered adding support for multi-query planners like PRM and PRMStar with reusable plan data?

[WaterHyacinthInNANHU]

I tried to modify ompl_planner.cpp to support PRM:

  // RRTConnect
  // auto rrt_connect = std::make_shared<og::RRTConnect>(si_);
  // if (range > 1E-6) rrt_connect->setRange(range);
  // planner = rrt_connect;

  // PRM
  auto prm = std::make_shared<og::PRM>(*stored_planner_data_);
  planner = prm;

  ss_->setPlanner(planner);
  ss_->setup();
  ob::PlannerStatus solved = ss_->solve(time);
  if (solved) {
    if (verbose) print_verbose("Found solution");

    // Store planner data for future reuse
    stored_planner_data_->clear();
    stored_planner_data_ = std::make_shared<ob::PlannerData>(si_);
    planner->getPlannerData(*stored_planner_data_);

But when I test it with test_planner.py, it fails:

1. Fails given a random target pose.
2. Segment fault when reusing the planner to plan more than once. (The PlannerData reuse part may be problematic)

Any suggestions are appreciated!