- set measurement of first sample to -1 to indicated that the data
is not valid

- give an estimate of the sensor variance based on the sensor resolution
and experiments

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

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

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

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

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

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

Move RC and DL failsafe actions handling from navigator to commander (credits to @AndreasAntener)
Separate manual kill switch handling via manual_lockdown to prevent override and release of software lockdown by RC switch

Other changes:
Add failsafe tune
Fix LED blinking for Pixracer
Return back support for rc inputs in simulator but now it is configurable via cmake

This disables the safety switch when Pixracer is configured. It does not change existing setups and it can be re-enabled after. This might be the more sensible default for a racing board.

this fixes a race condition between the DMA completion handler
updating registers in px4io and the mixer used for handling the
override state. The register set code could set r_page_servos[]
between the time when pwm_limit_calc() is called and the servos are
actually output.

  - Run in a single ssh command
  - Allow to update firmware when mavlink-routerd had already been
    stopped
  - Be resilient to another daemon interfering the communication by
    reading/writting to the UART
  - Print OS, BIOS nad FPGA version

mavlink_bridge.py script was removed in favor of new mavlink-router
project (https://github.com/01org/mavlink-router).

  - Other channels are irrelevant since they aren't physically
    connected. Avoid the I2C transaction to get invalid data
  - Port the driver to use only one address, as it should be
  - Minor changes here and there
  - Add test() method to read the latest value - helpful during
    debugging.

Measure the battery voltage of Aero RTF kit will be done by FPGA
and read by AeroFC using I2C bus.

The protocol is a little bit odd, it have different I2C slave
address for each "register", in future the FPGA RTL will
have a protocol more similar to other I2C sensors.

Also Aero RTF don't have a ADC line to measure current consumption.

We check if the target is SITL and do not build it with all other
posix targets.

Implement the way to run posix simulator directly from IDE without the need to reconfigure command lines, but use runner created via CMake

Steps to debug:
 * Run gazebo (or any other sim) server and client viewers via the terminal: `make posix_sitl_default gazebo_none_ide`
 * In your IDE select `px4_<mode>` target you want to debug (e.g. `px4_iris`)
 * Start debug session directly from IDE

This approach significantly reduces the debug cycle time because simulator (e.g. gazebo) is always running in background and you only re-run px4 process which is very light.

  * Loosen thresholds for gyro consistency check until temperature compensated units are the norm
  * Cut down string lengths so they make it through the MAVLink transport as a whole

This change makes the mixer load and reset operation closer to thread-safe. It was guarded one-way before and in only one location. This change ensures that its being locked out from both directions. The accesses to the locking variables still need work because they are non-atomic.

This change makes the operation more robust as it flags the whole group invalid in the first step. This should not be confused with being thread-safe - to be thread-safe, all accesses to _first and the following linked list need to be guarded by a mutex. This should be done outside of the mixer in the driver though, as the method depends on the board architecture.

UAVCAN: Make GPS module use the multi-topic facility so that a normal GPS and an UAVCAN GPS can co-exist and do not write on top of each other.