° use an event system instead of polling to track battery power loss
Merge branch 'chibios' of github.com:enacuavlab/paparazzi into chibios
° fix task priorities so that pprz has priority over others process
° fix adc sampling frequency : sample at high frequency for poweroff detection
  but fill sampling buffer at low fraquency according to previous pprz behavior
Merge branch 'chibios' of github.com:enacuavlab/paparazzi into chibios