hash check and heartbeat forwarding

- hash check disabling: for systems where a companion link forwards messages
to QGC (e.g. via LTE) parameter streaming will be stopped as soon as QGC
sends the request to stop the stream. If the companion side for some reason
still requires the stream to be active we need to disable QGC from stopping
the stream. Normally dronekit should be responsible for filtering out the
request from QGC but apparently this is not possible.

- disable heartbeat forwarding: dronekit does seem to get confused if
heartbeats from another system other than the autopilot get forwarded to it.
Example: Sending messages from QGC via the autopilot to dronekit running on
companion computer.

Signed-off-by: Roman <bapstroman@gmail.com>

The previous removal of the mag was not complete. It just disabled publishing. This commit conditionally removes all the the mag functionality.

looking at height rates

Signed-off-by: Roman <bapstroman@gmail.com>

    - devices in PX4/Firmware (8158cdfc): https://github.com/PX4/GpsDrivers/commit/aef48b04ff9b95350c4e5e507eea72a9e971d6a4
    - devices current upstream: https://github.com/PX4/GpsDrivers/commit/657514b26a0bf1b1ea2bf723b18449b04248822c
    - Changes: https://github.com/PX4/GpsDrivers/compare/aef48b04ff9b95350c4e5e507eea72a9e971d6a4...657514b26a0bf1b1ea2bf723b18449b04248822c

    657514b 2018-08-02 Alexis Paques - Adding UBX_MSG_RTCM3_* for additional messages
f9cf788 2018-08-02 Alexis Paques - Adding RTCM3 class documentation reference
6009a29 2018-08-02 Alexis Paques - Adding RTCM3 available output message IDs

- yaw_valid flag was always left at false which made the position controller reject the yaw setpoint of the reposition command

These leaks are not critical but the address-sanitizer complains.
And it's better programming practice anyway.

Signed-off-by: Lukas Woodtli <woodtli.lukas@gmail.com>

This allows a simple-to-use bootloader update mechanism to switch from
fmu-v2 to fmu-v3 target that has more flash.

- this ensures that the MAV_TYPE parameter is always updated
- previously it could happen that the simulator module was using a wrong
MAV_TYPE value because it only read the parameter value at initialisation

Signed-off-by: Roman <bapstroman@gmail.com>

   The update check is on ORB_ID(safety) but the copy
   was from ORB_ID(actuator_armed).

   Accept PWM_SERVO_[ENTER|EXIT]_TEST_MODE as a noop.
   As long as the mixer in passthrough and armed the
   pwm test will work.

   A hardfault was happening on:
    fmu stop
    fmu mode_pwm
    pwm info

   The _mixer was null and being dereferenced to access the trim
   setting that were moved to the mixer from the fmu.

   This commit fixes that but making the getter issue a warning
   and the setter fail.