message: Add const overloads of RobotPool methods
diff: @@ -38,6 +38,10 @@ public:
  DozerList& dozers() { return mDozers; }
  MinerList& miners() { return mMiners; }
  + const DiggerList& diggers() const { return mDiggers; }
  + const DozerList& dozers() const { return mDozers; }
  + const MinerList& miners() const { return mMiners; }
  +
  void clear();
  void erase(Robot* robot);
  bool insertRobotIntoTable(RobotTileTable& robotMap, Robot* robot, Tile* tile);
  