AP_Vehicle: added new header for parameters in multiple libraries

this adds a header where we can put vehicle specific parameters that
will be used in multiple libraries
AP_SpdHgtControl: removed AircraftParameters
AP_TECS: changed to AP_Vehicle.h
DataFlash: changed to AP_Vehicle.h
AP_Mount: changed to AP_Vehicle.h
AP_InertialNav: changed to AP_Vehicle.h
AP_HAL_AVR: changed to AP_Vehicle.h
AP_Airspeed: changed to AP_Vehicle.h

also allow updates to ARSPD_RATIO from user while autocal is running
AP_AHRS: changed to AP_Vehicle.h
APM_Control: changed to AP_Vehicle.h
AC_Fence: changed to AP_Vehicle.h
VARTest: changed to AP_Vehicle.h
Plane: changed to AP_Vehicle.h
Copter: changed to AP_Vehicle.h
Rover: changed to AP_Vehicle.h