[feat][refact] Update loop closure

This MR contains updates for the loop closure detection part:

--------In SLAM------

• Create a new structure of LoopIndices containing QueryIdx, RevisitedIdx and Time

• A vector LoopDetections of LoopIndices to is added in SLAM to store detected loop indices. This vector can be filled with a external csv file which contains loop indices. Or it can be filled with detected loop indices by function DetectLoopClosureIndices.

  Function AddLoopClosureIndices is added to fill this vector.

• DetectLoopClosureIndices becomes a public function which is a wrapping function of loop detection methods. (Only teaser++ for now, other loop closure detection methods will be added in the future.)

--------In PV wrapping------

• Add LoadLoopDetectionIndices function to load loop closure indices from a csv file.

  A helper function CreateCSVLoader is added

• Add DetectLoop function. Users can trigger a detection via button detect loop. If a loop is detected, indices are added into vector LoopDetections. They can be used for pose graph optimization.

• Some refacts for the interface

Here is a demo which shows the pose graph optimization with loop closure. The loop indices are loaded from an external csv file.