[refact][fix] Update external sensors

• Fix Calibration application on landmarks
• Clean SLAM API removing not used SLAM members
• Add reset function for external sensors
• Add functions to get measures in different frames or tracking different point
• Update documentation in external sensors
• Change IMU manager type to ImuGravityManager and name to GravityManager for further IMU implementations
• Add verbosity as sensor member
• Add macros to simply code in SLAM manager
• Add command to swith on/off external sensors in ROS
• Fix covariance rotation and add default covariances in case of degenerated ones
• Add parameter for number of iterations during pose graph optimization + add robustifier to remove outliers