Open source/feature/rviz display

[ToniRV]

• Allow registration of different Visualizer and Display modules: this is so that ROS visualization plays nicely with Kimera:
• Make Display and Visualizer of opencv inherit from base classes. (same for input/output packages).
  Swap modules upon user request
• Separate Display.h into the opencv and its parent class (now they are in the same file).
• Separate Visualizer.h into the opencv and its parent class ( now they are in the same file).

[violetteavi]

Note: This branch breaks at compile time with current Kimera-VIO-ROS master with this error:

/home/andrew/catkin_ws/src/Kimera-VIO-ROS/src/RosDataProviderInterface.cpp: In member function ‘virtual bool VIO::RosDataProviderInterface::publishSyncedOutputs()’:
/home/andrew/catkin_ws/src/Kimera-VIO-ROS/src/RosDataProviderInterface.cpp:226:45: error: ‘visualizeMesh2D’ is not a member of ‘VIO::Visualizer3D’
         cv::Mat mesh_2d_img = Visualizer3D::visualizeMesh2D(

It does compile with this Kimera-VIO-ROS branch. I will run a manual test on the two branches using the RealSense IR dataset and report back.