* AE improvements
* boardd: also use gain to compute IR brightness
* use default rect for DM autoexposure
* more smooth
* whitespace
* camerad cpu usage
* hcg on is slightly better for noise
* hysteris around high conversion gain
* improve i2c timing
* use AB contexts
* HCG default off
* run at 10 hz
* stay in context A for now
* remove ae thread
* wait till next frame is started before sending i2c
* back at 20fps
* add comment and filter across 3 evs
* remove context switch code
* tuning
* recomened without HCG is 0.8x
old-commit-hash: 25de93d133c386c353155c2b782e3807c46150cd