Barometer climb rate must be -150cm/s ~ +150cm/s
This threshold is generous because we already use the inertial
navigation climb rate so this is just to catch cases where inertial nav
is very incorrect in it's climbrate estimates

This corrects a bug that allowed the waypoint speed to be set to zero

fixes issue in which now could be earlier than _last_update_xy_ms
leading to a large dt value and a sudden lean on takeoff

This will help prevent spurious alt disparity warning messages for copter

Issue discovered and fix contributed by Deadolous

This resolves the issue of the parachute servo's position not being
initialised to the off position due to an ordering problem of the
auxiliary servos being initialised after the parachute object.

use compass.set_offsets() to avoid trying to write to storage

this will be used by Replay to prevent the need for saving parameters

Also return false when logging disabled

Triggers an "ekf" failsafe if the DCM yaw error is > 60deg

this ensures the wrapping of yaw is consistent between the 3 use cases

The DCM drift correction code uses the current attitude to calculate
error values to update its gyro drift correction. If we were using EKF
then without this patch the DCM code running as an alternative AHRS
source would be using the EKF attitude for calculating the error
value, leading to very bad gyro drift estimation

use_compass() and reset() are common to AP_AHRS_DCM and
AP_AHRS_NavEKF. As AP_AHRS_NavEKF is a child of AP_AHRS_DCM, when we
call use_compass() from within AP_AHRS_DCM we actually end up calling
AP_AHRS_NavEKF::use_compass().

This has the effect of disabling the compass in DCM when EKF is active
and EKF has decided not to use the compass. That means that the DCM
yaw (and in fact the whole attitude) can get badly off while EKF is
enabled, making DCM an ineffective fallback if EKF fails.

The fix is to call the specific class versions of use_compass() and
reset()

Fixes issue in which user only had 5 seconds after starting auto-trim to
raise the throttle before the auto-disarm would kick-in.

this prevents a floating point error caused by using an uninitialised
vector3 when switching between DCM and EKF control in AP_InertialNav

Pair-Programmed-With: Randy Mackay <rmackay9@yahoo.com>

This returns true if the gyros have been calibrated successfully

Spotted by Jonathan Challinger, thanks!

Also trigger throttle_upper flag when throttle in reaches 1000

limit.throttle_lower flag becomes true when the throttle passed into the
motors lib (which is in the 0 ~ 1000 range) is below _min throttle.
This makes the interpretation of the THR_MIN parameter consistent
between the main code (which uses 0 ~ 1000 range) and the motors lib
(which previously used the RC3_MIN ~ RC3_MAX range).
The remaining problem however is that the output of the motors continues
to use THR_MIN as if it were a pwm.  I don't believe this is a dangerous
problem however.

Rate D max to 0.020 (was 0.015)
Rate P max to 0.35 (was 0.25)
Stab P max to 20 (was 15)