- EKF2 airspeed fusion and synthetic sideslip fusion
 - commander eph/epv failsafe thresholds appropirate for FW

    - Changes: https://github.com/PX4-NuttX/nuttx/compare/fe0dc6c41a6bd7d942945459ac960ff2d3e1f4fc...65b87d092a6d5f776ab5f9dbb095d31e45861789

    65b87d0 2018-04-19 Daniel Agar - [PX4 BACKPORT] Merged in dagar/nuttx/pr-stm32f777_typo (pull request #628)

- useful for tuning snapdragon flight

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

 * ECL update includes physical constants for https://github.com/PX4/Firmware/pull/9319

Signed-off-by: CarlOlsson <carlolsson.co@gmail.com>

Signed-off-by: CarlOlsson <carlolsson.co@gmail.com>

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

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

- reduce height increase during front transition

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

- the mc pos controller will decrease throttle during the transition
and thus the vehicle will not pick up enough airspeed to complete the
transition

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

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

- removing unused variables
- removing unused code blocks
- improving code readability
- initialising members at definition

An airframe change keeps all RC params except the flight modes. This fixes
that.