Improve accuracy using IMU

[eperdices]

Current RGB-IMU Fusion doesn't improve Monocular SLAM accuracy. It should be reviewed to extract more orientation information from IMU data.

[eperdices]

Right now, there is an EKF inside SD-SLAM for IMU data fusion. It does not work very well and it even harms SD-SLAM accuracy.

There are several algorithms already implemented in ROS for IMU fusion, it is worth it to try to use these algorithms and remove our own EKF fusion:

• http://wiki.ros.org/imu_filter_madgwick
• http://wiki.ros.org/imu_complementary_filter