AP_Compass: added vector compass setHIL method
AP_NavEKF: initial test sketch for NavEKF
AP_NavEKF: added dataflash log reader

this gives log playback into HIL
Cleaned formatting and explicitly defined numerical values and trig operators as floats
AP_NavEKF: cleanup header, adding comments
AP_NavEKF: added euler angle functions
AP_NavEKF: try running EKF on log data