Copter: disarm on land even if pilot throttle not zero

default behaviour remains as before, this is an compile time option only
Tools: we don't have AP_NavEKF.h yet
Copter: add support for MAV_CMD_DO_SET_SERVO
Copter: simplify do-set-servo mission command

This potentially changes the servo number that must be supplied if using
an APM1 but it now shares the same logic as arduplane and also adds
protection that the servo is not attached to the motor.
removed debug message from previous commit.
AC_WPNav: accessor for loiter speed
Copter: allow ch6 tuning of loiter speed
HAL_PX4: use eeprom on PX4 FMUv1 as well

this means we no longer store params on SD at all
PX4: enable MTD on FMUv1 as well
AP_HAL: added set_safety_pwm() API
HAL_PX4: implement set_safety_pwm() API

used to set PWM on motors when disarmed
Plane: setup PWM to be used on throttle when safety is safe on PX4
Merge remote-tracking branch 'diydrones/master' into master_new