To run:
cd src/lib/mixer
make tests

This will validate the C++ implementation by taking the python
implementation as ground-truth. It runs through various actuator control
command values for all airmode variations and several mixer types.

The python script also allows to prototype new mixer algorithms.

It is not integrated into the existing build system, because it's easier
to use that way, with less dependencies, and faster testing workflow.
It could however be a bit more integrated.

Reference: https://github.com/Auterion/Flight_Control_Prototyping_Scripts/tree/master/control_allocation

- avoid including <px4_defines.h> from the math headers
- avoid driver include <drivers/drv_mixer.h> from the mixer

Provides a more generic desaturation algorithm, making it easier to
handle the different mixer strategies.

python reference implementation:
https://github.com/Auterion/Flight_Control_Prototyping_Scripts/tree/master/control_allocation

The behavior for non-airmode and roll/pitch airmode should be the
same as before.

CPU load is slightly higher for the non-airmode case (+0.5%), for airmode
it is the same.

_Stof, bsearch, param_find_changed

- landing_gear: refactor state name
- Add the keep state to the landing gear message
- Adapt FlightTaskManual, FlightTaskAutoMapper, mc_pos_control,
to review message definition

 * fixes parameters on Snapdragon

FlightTaskAutoLine: ensure that desired speed along track does not exceed maximum speed at threshold to target

    - matrix in PX4/Firmware (4005de7b9600db8a310d52f9bf7a47a0019868d8): https://github.com/PX4/Matrix/commit/0d3bff5e006cfaa358b51e3a6d11984e3782a90e
    - matrix current upstream: https://github.com/PX4/Matrix/commit/9c0acfba36a928b7b002eea3a9dca54a5a0c1250
    - Changes: https://github.com/PX4/Matrix/compare/0d3bff5e006cfaa358b51e3a6d11984e3782a90e...9c0acfba36a928b7b002eea3a9dca54a5a0c1250

    9c0acfb 2018-11-20 Matthias Grob - Matrix: remove unsafe copyToRaw method