- accel & gyro FIFOs enabled
- FIFO watermark on data ready interrupt
- sensor side filtering completely disabled
- gyro now respects `IMU_GYRO_RATEMAX` (up to 2 kHz)
- saves a few % cpu (at default rate)
- always check with state machine before reboot/shutdown
- respect BOARD_HAS_POWER_CONTROL (shutdown from command, low battery, power button)
- px4_shutdown_request add optional delay and always execute from HPWORK
- px4_shutdown_request split out px4_reboot_request