- include icm20948 on most boards by default
- create more test variants for default boards near flash limit (cuav_nora_test, cuav_x7pro_test, holybro_durandal-v1_test)
- simple state machine to reset, configure, etc
- checked register mechanism (sensor will reset itself on configuration error)
- configured in 16 bit mode (1320 LSB/Gauss instead of 330 LSB/Gauss)
- adjusted orientation handling in driver to match datasheet as closely as possible
- in many external compass units the rotation was wrong and very difficult to actual determine how to set correctly
- 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
