Removed multithreading ifdef from header
Filter3D: Stubs
Filter3D: Initial Kalman filter prototype
Filter3D: Replace angle-axis with quaternion representation in state
Filter3D: Updated TODO note for memcpys
Filter3D: Enable/disable API
Filter3D: Added sample
Filter3D: IMU API preview
Filter3D: Separate prediction/correction and process IMU input
Filter3D: Refactored filter init and quat conversion
Filter3D: Apply filter enable/disable to prediction as well
Filter3D: Refactored conversion to quaternion
Filter3D: Array access refactoring