不積跬步之IMU預積分

IMU預計分論文：On-Manifold Preintegration for Real-Time Visual-Inertial Odometry(http://arxiv.org/abs/1512.02363)

IMU初始化論文：Visual-Inertial Monocular SLAM with Map Reuse(https://arxiv.org/abs/1610.05949)