Plane: added DF logging of 2nd battery voltage
Replay: fixed build with AP_NavEKF API change
Copter: minor update to AC3.2-rc14 ReleaseNotes
Camera: Added feedback message support

Now the autopilot can publish the state of the camera via the mavlink_msg_camera_feedback message.
GCS_MAVLink: add CAMERA_FEEDBACK to enum
Copter: send a camera_feedback message when there is a camera trigger
Camera: record number of pictures taken since boot

The field is useful for detecting in a GCS if a mavlink_msg_camera_feedback message was dropped.
Copter: fix camera feedback msg handling

If the camera was disabled, camera message handling would fall though to
status-text msg handling.
Camera: initialise image_index
Camera: add f to float constants
AC_WPNav: Use target yaw instead of current yaw for close waypoints
Copter: supply wp_nav with attitude_control
Copter: rework control switch debouncing
Copter: add comments to control switch debouncing
Copter: re-order init_sonar

No functional change.
ArduPilot: update README.md
ArduPilot: fixup README format
AP_InertialSensor: fixed default MPU9250 orientation for NavIO
AP_TECS : Prevent throttle undershoot after climb

If the plane was unable to achieve the climb and got significantly below the internal TECS demanded climb profile, the the PD term would be a large value at the top of climb, and would take some time to reduce due to the rate limiter. This meant that the integrator state could be pushed to a very low value and effectively cause the throttle to sit on the lower limit for longer than desired after levelling out.
AP_TECS: fixed throttle demand on underspeed

thanks to Philipp Oettershagen for finding this bug!