Fixed a potential bug in analog sensor management

- Associated pin is now initialized as input in constructor
Modified cameras behaviour


- experiencing some unexpected shutdown with camera after several 
minutes of activity, cameras are now used only in video mode and videos
are splitted every 2 minutes. In medium ascending phase (between 3000m
and 20000m), cameras are powered off most 66% of the time.
Added a compensation when calculating system time

- millis() did not seem to be very accurate
Cleaned comments
Added a debugInfo function

- provide an easy way to send debug info on both serial and radio link