Renamed IMUFilter to OdometryFilter because it's not filtering the raw
IMU, it's performing a transform to Odometry
Added new header defining the interface for the IMUFilter class which
will be used to EKF the raw IMU data from the sensor
Renamed all of the state constants so that they reflected the fact that
they were for Odometry matricies. Added state constants for the IMU
state matrix
Added start of implementation of the IMUFilter class