- partially addresses #11017

_Stof, bsearch, param_find_changed

- Use the values from landing_gear.msg

- Handled in the flight task

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

- Addressing review comments

- It takes the input from the constrains from the active flight task

- An new message is created just for the landing gear
- The old logic is repalaced by publishing this new topic

Keeps things more modular.

 * fixes parameters on Snapdragon

* added a parameter for enabled the smart battery
* start tel1 and tel2 at 921600 and max rate
* turned up the max tx rate on mavlink streams for telem1 and telem2
* turned off mavlink stream for tel1 in 4250_teal. This is connected to TX1 FTDI UART and has issues.
* moved check to 4250 board ID to start mpu9250s for Teal airframe into fmuv4 rc.board.

 - fixes #10980

    - nuttx in PX4/Firmware (eddfa7421c4ca2eb0969498093e09fa834e920bd): https://github.com/PX4/NuttX/commit/166d898c70141d7ddb179b5ead1c5ea726574411
    - nuttx current upstream: https://github.com/PX4/NuttX/commit/d07a1d459ee9b5b56dbf06a160e8faa4c49fcd10
    - Changes: https://github.com/PX4/NuttX/compare/166d898c70141d7ddb179b5ead1c5ea726574411...d07a1d459ee9b5b56dbf06a160e8faa4c49fcd10

    d07a1d4 2018-12-04 Beat Küng - [REJECTED] arm/include/math.h: remove _PARAMS macro (#42)

* Integrated preliminary ICM20948 support into MPU9250 driver.
Fixed temperature conversion for MPU9250/ICM20948.
* Included missing check for PX4_I2C_OBDEV_MPU9250 in main.cpp.
* Added explicit bus for internal MPU9250 on Pixhawk 2.1 to avoid implicit start
of an externally attached device with wrong orientation.